Comparative Evaluation of Embedded Heating Elements as Electrothermal Ice Protection Systems for Composite Structures

Since the development of modern aviation, the formation of ice on aerodynamic surfaces has been an important topic of study. It has been most critical in aviation because icing accidents have a high probability of being fatal. In energy production applications, such as wind turbines, blade icing can reduce power production efficiency and increase structural loads. Active ice protection systems have thus been developed using mechanical, thermal, or chemical methods. The thermal method is the only one that can both prevent and remove ice formations. Nowadays, hot air (i.e., bleed air from engines) thermal ice protection is used for commercial aircraft primary structures that are composed of metals. Composite structures are more suited to electrothermal ice protection systems than to hot air technology because bleed air is too hot and can cause structural damage to the composite. Design criteria for electrothermal systems heavily stand or fall on heating elements’ properties. Thus, within this work a study was conducted on the thermal efficiency, and temperature uniformity with consideration for manufacturability, availability, and potential impact of physical properties of three different heating element materials: constantan, carbon fiber, and carbon nanotube networks. Tests were performed on flat heater coupons in an icing wind tunnel. Infrared surface temperature measurements and de-icing time measurements revealed that the performance of the different materials did not differ considerably if all were driven by the same nominal power. Rather, the line spacing between the heating elements was the dominant influencing factor

Optimisation dynamique de la sélection de vols partagés d'un transporteur aérien

RÉSUMÉ Le partage de vols est une pratique désormais très répandue qui permet à un transporteur aérien d’apposer un de ses numéros de vol sur un vol exploité par une compagnie partenaire pour ainsi considérer ce dernier dans son propre réseau. Malgré qu’il ait été prouvé à maintes reprises que ce type de partenariat peut générer d’énormes revenus additionnels, il reste très complexe pour une compagnie aérienne de choisir quels vols partager avec quels partenaires. L’objectif du présent projet est de proposer un outil d’aide à la décision qui optimise les revenus d’un transporteur aérien en considérant deux aspects qui n’étaient pas expressément considérés dans la littérature : l’impact de rendre un vol partagé dans le réseau et les interactions qui existent entre les vols que l’on souhaite rendre partagés. Pour ce faire, une méthode heuristique est développée. À chaque itération, la demande est répartie sur le réseau en fonction de la sélection de vols partagés et cette sélection est modifiée dans le but d’augmenter la profitabilité du transporteur. Pour accélérer la résolution, la demande est répartie sur des graphes réduits au lieu de considérer le réseau entier d’un transporteur. Un modèle mathématique de répartition de la demande est construit et validé à l’aide d’un logiciel existant afin d’être utilisé à l’intérieur de l’heuristique. De plus, une méthode de blocage du flot est employée pour assurer un plus grand réalisme. Deux algorithmes basés sur l’heuristique développée sont appliqués pour optimiser la sélection de vols partagés d’Air Canada avec un partenaire et, en deuxième temps, avec deux partenaires. En comparaison avec deux méthodes actuellement utilisées, ces algorithmes proposent des sélections de vol qui génèrent beaucoup plus de revenus. Les résultats obtenus démontrent également qu’il existe une interaction claire entre les vols partagés choisis et qu’il est important de considérer cet effet dans l’optimisation de la sélection de vols partagés. Toutefois, les algorithmes proposés nécessitent de très longs temps de résolution et rien n’assure leur convergence. Des recherches plus approfondies devront être menées pour accélérer la résolution de l’heuristique proposée, pour améliorer la précision du modèle de répartition de la demande utilisé et pour étudier plusieurs facteurs reliés à la gestion de vols partagés qui n’ont pas été considérés dans le présent projet.---------- ABSTRACT Codesharing is now a widespread practice that allows an airline to put one of its flight numbers on a flight operated by a partner airline and consider it in its own network. Even though it has been repeatedly demonstrated that this type of partnership can generate important additional revenues, it is very complex for an airline to choose which flights to share with which partners. The objective of this project is to provide a decision support tool that maximizes the revenues of an airline considering two aspects that were not explicitly considered in the literature: the impact of adding a shared flight in the network and the interactions that exist between flights that are chosen to become codeshared. Therefore, a heuristic is developed. At each iteration, the demand is distributed on the network considering the codeshare flight selection and this selection is modified in order to increase the profitability of the carrier. To speed up the resolution, the demand is distributed on reduced graphs instead of the full network. A mathematical model of demand distribution is built and validated using existing software before being used in the heuristic. In addition, a blocking flow method is used to ensure greater realism. Two algorithms based on the developed heuristic are used to optimize the codeshare flight selection of Air Canada with one partner and with two partners. In comparison with two methods currently used, these algorithms propose codeshare flight selections that generate much greater revenues. The results also show that there is a clear interaction between selected flights and that it is important to consider this effect when optimizing the selection of codeshared flights. However, the proposed algorithms require very long resolution times and their convergence is not guaranteed. Further research should be conducted to acccelerate the resolution of the proposed heuristic, to improve the accuracy of the demand distribution model used and to investigate different factors related to codeshare management that were not considered in this project

Performance of prognostic risk scores in chronic heart failure patients enrolled in the European Society of Cardiology Heart Failure long-term registry

[Abstract] Objectives. This study compared the performance of major heart failure (HF) risk models in predicting mortality and examined their utilization using data from a contemporary multinational registry. Background. Several prognostic risk scores have been developed for ambulatory HF patients, but their precision is still inadequate and their use limited. Methods. This registry enrolled patients with HF seen in participating European centers between May 2011 and April 2013. The following scores designed to estimate 1- to 2-year all-cause mortality were calculated in each participant: CHARM (Candesartan in Heart Failure-Assessment of Reduction in Mortality), GISSI-HF (Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico-Heart Failure), MAGGIC (Meta-analysis Global Group in Chronic Heart Failure), and SHFM (Seattle Heart Failure Model). Patients with hospitalized HF (n = 6,920) and ambulatory HF patients missing any variable needed to estimate each score (n = 3,267) were excluded, leaving a final sample of 6,161 patients. Results. At 1-year follow-up, 5,653 of 6,161 patients (91.8%) were alive. The observed-to-predicted survival ratios (CHARM: 1.10, GISSI-HF: 1.08, MAGGIC: 1.03, and SHFM: 0.98) suggested some overestimation of mortality by all scores except the SHFM. Overprediction occurred steadily across levels of risk using both the CHARM and the GISSI-HF, whereas the SHFM underpredicted mortality in all risk groups except the highest. The MAGGIC showed the best overall accuracy (area under the curve [AUC] = 0.743), similar to the GISSI-HF (AUC = 0.739; p = 0.419) but better than the CHARM (AUC = 0.729; p = 0.068) and particularly better than the SHFM (AUC = 0.714; p = 0.018). Less than 1% of patients received a prognostic estimate from their enrolling physician. Conclusions. Performance of prognostic risk scores is still limited and physicians are reluctant to use them in daily practice. The need for contemporary, more precise prognostic tools should be considered

Tuning static drop friction

The friction force opposing the onset of motion of a drop on a solid surface is typically considered to be a material property for a fixed drop volume on a given surface. However, here we show that even for a fixed drop volume, the static friction force can be tuned by over 30% by preshaping the drop. The static friction usually exceeds the kinetic friction that the drop experiences when moving in a steady state. Both forces converge when the drop is prestretched in the direction of motion or when the drop shows low contact angle hysteresis. In contrast to static friction, kinetic friction is independent of preshaping the drop, that is, the drop history. Kinetic friction forces reflect the material properties

Long‐term safety of intravenous cardiovascular agents in acute heart failure: results from the European Society of Cardiology Heart Failure Long‐Term Registry

[Abstract] Aims. The aim of this study was to assess long‐term safety of intravenous cardiovascular agents—vasodilators, inotropes and/or vasopressors—in acute heart failure (AHF). Methods and results. The European Society of Cardiology Heart Failure Long‐Term (ESC‐HF‐LT) registry was a prospective, observational registry conducted in 21 countries. Patients with unscheduled hospitalizations for AHF (n = 6926) were included: 1304 (18.8%) patients received a combination of intravenous (i.v.) vasodilators and diuretics, 833 (12%) patients received i.v. inotropes and/or vasopressors. Primary endpoint was long‐term all‐cause mortality. Main secondary endpoints were in‐hospital and post‐discharge mortality. Adjusted hazard ratio (HR) showed no association between the use of i.v. vasodilator and diuretic and long‐term mortality [HR 0.784, 95% confidence interval (CI) 0.596–1.032] nor in‐hospital mortality (HR 1.049, 95% CI 0.592–1.857) in the matched cohort (n = 976 paired patients). By contrast, adjusted HR demonstrated a detrimental association between the use of i.v. inotrope and/or vasopressor and long‐term all‐cause mortality (HR 1.434, 95% CI 1.128–1.823), as well as in‐hospital mortality (HR 1.873, 95% CI 1.151–3.048) in the matched cohort (n = 606 paired patients). No association was found between the use of i.v. inotropes and/or vasopressors and long‐term mortality in patients discharged alive (HR 1.078, 95% CI 0.769–1.512). A detrimental association with inotropes and/or vasopressors was seen in all geographic regions and, among catecholamines, dopamine was associated with the highest risk of death (HR 1.628, 95% CI 1.031–2.572 vs. no inotropes). Conclusions. Vasodilators did not demonstrate any association with long‐term clinical outcomes, while inotropes and/or vasopressors were associated with increased risk of all‐cause death, mostly related to excess of in‐hospital mortality in AHF

Durability of Superamphiphobic Polyester Fabrics in Simulated Aerodynamic Icing Conditions

Fabrics treated to repel water, superhydrophobic, and water and oil, superamphiphobic, have numerous industrial and consumer-level benefits. However, the liquid repellency decreases in the course of time. This is largely due to chemical or physical changes of the coating due to prolonged exposure to relatively harsh environments. To develop more durable fabric treatments for specific applications, it is necessary to measure the extent to which the treated fabrics retain their low-wettability after being subjected to controlled aggressive environmental conditions. In this study, plain weave fabrics made from polyester filaments and coated with silicone nanofilaments in-solution were exposed to aerodynamic icing conditions. The coated fabrics showed superhydrophobic behavior, or superamphiphobic for those that were fluorinated. The wettability of the fabrics was progressively evaluated by contact angle and roll-off-angle measurements. The coated fabrics were able to maintain their low-wettability characteristics after exposure to water droplet clouds at airspeeds up to 120 m/s, despite damage to the silicone nanofilaments, visible through scanning electron microscopy

Electrocardiographic features and their echocardiographic correlates in peripartum cardiomyopathy: results from the ESC EORP PPCM registry

Aims: In peripartum cardiomyopathy (PPCM), electrocardiography (ECG) and its relationship to echocardiography have not yet been investigated in large multi-centre and multi-ethnic studies. We aimed to identify ECG abnormalities associated with PPCM, including regional and ethnic differences, and their correlation with echocardiographic features. Methods and results: We studied 411 patients from the EURObservational PPCM registry. Baseline demographic, clinical, and echocardiographic data were collected. ECGs were analysed for rate, rhythm, QRS width and morphology, and QTc interval. The median age was 31 [interquartile range (IQR) 26–35] years. The ECG was abnormal in > 95% of PPCM patients. Sinus tachycardia (heart rate > 100 b.p.m.) was common (51%), but atrial fibrillation was rare (2.27%). Median QRS width was 82 ms [IQR 80–97]. Left bundle branch block (LBBB) was reported in 9.30%. Left ventricular (LV) hypertrophy (LVH), as per ECG criteria, was more prevalent amongst Africans (59.62%) and Asians (23.17%) than Caucasians (7.63%, P < 0.001) but did not correlate with LVH on echocardiography. Median LV end-diastolic diameter (LVEDD) was 60 mm [IQR 55–65] and LV ejection fraction (LVEF) 32.5% [IQR 25–39], with no significant regional or ethnic differences. Sinus tachycardia was associated with an LVEF < 35% (OR 1.85 [95% CI 1.20–2.85], P = 0.006). ECG features that predicted an LVEDD > 55 mm included a QRS complex > 120 ms (OR 11.32 [95% CI 1.52–84.84], P = 0.018), LBBB (OR 4.35 [95% CI 1.30–14.53], P = 0.017), and LVH (OR 2.03 [95% CI 1.13–3.64], P = 0.017). Conclusions: PPCM patients often have ECG abnormalities. Sinus tachycardia predicted poor systolic function, whereas wide QRS, LBBB, and LVH were associated with LV dilatation