Improving Product Design by Predicting Flexural Strength of a Honeycomb Core Sandwich Panel Composite Using Ply Tensile Strength

The use of composite sandwich panels has increased in the aerospace industry. Prediction of a theoretical composite construction\u27s flexural properties is important for efficient composite product designs. Utilizing the four point flexure geometry defined by Zodiac Aerospace, Santa Maria, CA, a mechanical model was derived to predict the flexural behavior of a theoretical honeycomb core sandwich composite using laminate tensile properties. The most common failure mode of Zodiac Aerospace’s four point bend test is a failure in tension of the bottom laminate. Given this information, ASTM D3039 (Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials) was chosen to test ply tensile properties. Based on the ASTM standard, a sample size of 30 specimens for each laminate was examined to account for any statistical variance. Specimen width was 1 inch, as suggested by the ASTM standard, and the thickness was 0.01 inches per ply on average. A high strength epoxy was used to adhere medium density fiberboard tabs to the fiberglass specimen to ensure failure occurred within the gage length. The tensile strength of a phenolic woven-fiberglass laminate construction with 1-ply, 2-ply, and 3-ply thicknesses was tested, inserted into the mechanical model, and compared to existing flexural data on sandwich panels tested by Zodiac Aerospace. The results indicate that the tensile strength increases as the number of plies are increased. The average tensile strength value for one, two and three ply are 38.8 ksi, 64.67 ksi and 71.22 ksi respectively. Although the flexural load of a sandwich panel with given dimensions was calculated using the ply tensile strength, the predicted loads may not be representative of the flexural loads measured in industry because the plies tested did not come from a population of batches, but from one batch

Sélection dynamique des services de vols durant l’optimisation des rotations d’équipages aériens

RÉSUMÉ : Une problématique importante tant sur le plan financier que mathématiques d’une compagnie aérienne est la fabrication des horaires pour son personnel. Ceux-ci doivent respecter les contraintes légales ainsi que celles des conventions collectives. Alors que d’autres contraintes s’ajoutent à celles-ci, comme la satisfaction des employés qui est considérée dans la fabrication des emplois du temps pour certaines compagnies, nous aboutissons déjà à des problèmes de très grande taille parmi ceux du domaine de la Recherche Opérationnelle. Ils sont séparés en plusieurs problèmes d’optimisation résolus séquentiellement, dont l’un est au centre du travail de ce mémoire : la fabrication de rotations. Ce problème consiste à générer des rotations pour l’équipage de la compagnie à partir de services de vols. Nous appelons une rotation une partie d’un emploi du temps d’une durée variant généralement de 2 à 6 jours, partant et revenant à la base de l’équipage, et l’enchaînement de deux rotations est généralement séparé par une période de repos spéciale. Un service de vol est une séquence de vols séparés par des connections, effectué par un même équipage sur une durée d’une journée de travail. L’objectif à cette étape est de générer des rotations de faible coût, respectant toutes les contraintes, et dont nous pouvons sélectionner un sous-ensemble de coût minimal qui nous permette d’effectuer toutes les taches prévues, comme les vols à assurer. Elle se résout souvent, et c’est le cas dans ce mémoire, à l’aide d’une méthode de génération de colonnes. Cette génération est difficile car il y a une grande "dimension" combinatoire : le nombre de possibilités de concevoir une rotation à partir d’une séquence de services de vols est trop important pour que l’on imagine toutes les générer. Plusieurs techniques d’accélération de la résolution par génération de colonnes existent pour le problème maître (agrégation de contraintes, perturbation, stabilisation) comme pour les sous-problèmes (comme avec des algorithmes de programmation dynamique qui utilisent seulement des sous ensembles des arcs et des étiquettes). Dans le cas d’une résolution avec étiquettes pour la résolution, ce qui est actuellement généralisé, nous proposons d’utiliser les informations duales que nous pouvons récupérer de celles-ci afin de développer un critère de sélection dynamique d’arcs. Ainsi capable de sélection, nous présentons dans ce travail de maîtrise une nouvelle résolution du problème de génération de rotations par génération de colonnes. Nous réduisons le nombre d’arcs des sous-problèmes de plus de 80% pour constituer une banque d’arcs dans laquelle nous sélectionnons dynamiquement ceux que nous avons intérêt à ajouter dans les réseaux des sous-problèmes. Un logiciel de planification développé chez AdOpt, division spécialisée dans le transport aérien de la compagnie Kronos, appelé Altitude Pairing, est dédié à cette étape d’optimisation. Nous y avons implémenté le module développé, en s’attachant à le faire de façon modulaire ce qui permettra le développement de nouveaux outils sur cette base prometteuse. Cette implémentation a demandé une adaptation des concepts théoriques aux réalités du code. Les résultats montrent sur les jeux de données auxquels nous avons eu accès une diminution supérieure aux deux-tiers des temps de calculs dans les sous-problèmes, mais une augmentation du temps global de résolution : l’augmentation du temps de ré-optimisation du problème maître n’est pas suffisamment compensé par le temps gagné dans les sous-problèmes. Pour faire face à ce problème nous avons implémenté et testé deux modifications : la première consiste à relâcher le critère de sélection des arcs. La seconde est de limiter le nombre d’itérations en la banque d’arcs mise-à-jour et le réseau courant. Nous décidons de cette façon d’avoir moins d’itérations d’ajouts d’arcs, tout en augmentant le nombre d’arcs ajoutés. Cela démontre l’intérêt de cette méthode qui devra être testé sur des jeux de données plus complets à l’avenir, ainsi qu’être mieux intégrée dans la stratégie de résolution.----------ABSTRACT : One of airline industry’s major financial and mathematical issue is scheduling. An airline schedule has to comply to a lot of legal constraints and labor agreements. Without considering other additional constraints, we already are facing a huge optimization problem. This one is traditionally separated in several sequential optimization problems, among which is the one considered in this Maîtrise: pairing generation. This problem’s objective is to generate pairings for airline personnel from duties. A pairing is part of a schedule, usually lasting from 2 to 6 days, starting and ending at the crew’s designated base, and two pairings usually have a special rest inbetween. a duty is a flight sequence inbetween connections, that are flown by the same crew and lasts one day. Here we have to generate pairings with low costs, that comply with all constraints, and enabling us to covering each and every flight that is scheduled, using a sub-set of them. It is often solved using column generation techniques, as it is in this present work. It is a hard generation because of the huge number of possibilities to generate a sequence of duties from a set of duties. In fact, we won’t be able to generate all of the possible pairings because there are way too many. Several acceleration techniques are used for column generation, from master problem (constraints aggregation, perturbation or stabilization) to sub-problem (labelling algortihm for example). In this latter case, which is nowadays used a lot, we suggest to use dual informations from these labels, aiming to create a criteria for a dynamique selection of arcs. Now capable of selecting arcs according to this criteria, we present a new resolution of pairing generation using column generation. We use reduced subproblems networks with at most 20% initial arcs, the other put into a "bank". From this bank will be dynamically selected interesting arcs to subproblems networks. A dedicated software developped at AdOpt, specialized division in airline transportation industry of company Kronos, is called Altitude Pairing. We implemented in it our module, making sure all the processus would be modular. This is necessary so that our tools can be used in the future. Results show that on our three data sets, time spent in subproblems was reduced but that the Master Problem resolution took longer which led to an overall resolution time also longer. The subproblem time improvement did not compensate for the deterioration of the Master Problem time resolution. To overcome these difficulties, we decided to implement two main modifications: relax our criteria that determines if an arc can lead to an interesting column or not, and limit the number of dynamic arc adding. We thus enable our algorithm to add more arcs but less frequently. These modifications led tovery positive results: we reached a better end value in a shorter time. This demonstrates this method’s quality: it still has to be tested on bigger data sets, and the overall resolution strategy has to be adapted to this new module in a better way

Comparative assessment of heat tolerance in weevils associated with a fire-prone ecosystem

Fire is an important cause of disturbance that directly shapes many ecosystems worldwide, the frequency and intensity of which are expected to increase with climate change. While the effect of fire on floristic dynamics has been widely documented, little is known about how phytophagous insects respond when facing these disturbances. We explored the survival strategies of a set of sixteen weevil species with divergent lifestyles and geographic distribution in fire-prone ecosystems of the Cape Floristic Region (South Africa). More specifically, we investigated how the lifestyle of species correlated with heat tolerance. For instance, wingless species were hypothesized to show higher heat tolerance as they have a limited ability to escape fire and usually remain hidden in the soil. The thermal tolerance of the insects was first measured using a standard heat knockdown set-up. Thermo-limit respirometry was then performed on the most resistant species using a thermal ramping protocol. Our results show that weevils exhibit high variation in thermal tolerance across taxonomic groups. Species ecology better explains thermal tolerance than flight ability or the fire-proneness of ecosystems. Furthermore, some non-flying weevil species were found to be highly heat tolerant with CTmax values reaching up to 51.9°C. This study highlights the diversity of strategies developed by arthropods to escape extreme heat in fireprone ecosystems. Further work is necessary to examine the generality of these patterns across other fire-prone ecosystems to better understand behavioural compensation and evolutionary responses

Phosphatidylinositol 3-phosphate mediates the establishment of infectious bursal disease virus replication complexes in association with early endosomes

Infectious bursal disease virus (IBDV) is the archetypal member of the family Birnaviridae and the etiological agent of Gumboro disease, a highly contagious immunosuppressive infection of concern to the global poultry sector for its adverse health effects in chicks. Unlike most double-stranded RNA (dsRNA) viruses, which enclose their genomes within specialized cores throughout their viral replication cycle, birnaviruses organize their bisegmented dsRNA genome in ribonucleoprotein (RNP) structures. Recently, we demonstrated that IBDV exploits endosomal membranes for replication. The establishment of IBDV replication machinery on the cytosolic leaflet of endosomal compartments is mediated by the viral protein VP3 and its intrinsic ability to target endosomes. In this study, we identified the early endosomal phosphatidylinositol 3-phosphate [PtdIns(3)P] as a key host factor of VP3 association with endosomal membranes and consequent establishment of IBDV replication complexes in early endosomes. Indeed, our data reveal a crucial role for PtdIns(3)P in IBDV replication. Overall, our findings provide new insights into the replicative strategy of birnaviruses and strongly suggest that it resembles those of positive-strand RNA (1ssRNA) viruses, which replicate in association with host membranes. Furthermore, our findings support the role of birnaviruses as evolutionary intermediaries between 1ssRNA and dsRNA viruses and, importantly, demonstrate a novel role for PtdIns(3)P in the replication of a dsRNA virus. IMPORTANCE Infectious bursal disease virus (IBDV) infects chicks and is the causative agent of Gumboro disease. During IBDV outbreaks in recent decades, the emergence of very virulent variants and the lack of effective prevention/treatment strategies to fight this disease have had devastating consequences for the poultry industry. IBDV belongs to the peculiar family Birnaviridae. Unlike most dsRNA viruses, birnaviruses organize their genomes in ribonucleoprotein complexes and replicate in a core-independent manner. We recently demonstrated that IBDV exploits host cell endosomes as platforms for viral replication, a process that depends on the VP3 viral protein. In this study, we delved deeper into the molecular characterization of IBDV-endosome association and investigated the role of host cell phosphatidylinositide lipids in VP3 protein localization and IBDV infection. Together, our findings demonstrate that PtdIns(3)P serves as a scaffold for the association of VP3 to endosomes and reveal its essential role for IBDV replication.Fil: Gimenez, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentina. University of Toronto; CanadáFil: Issa, Mariam. University of Toronto; CanadáFil: Sheth, Javal. University of Toronto; CanadáFil: Colombo, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Terebiznik, Mauricio R.. University of Toronto; CanadáFil: Delgui, Laura Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin

The effect of oxygen limitation on a xylophagous insect's heat tolerance is influenced by life-stage through variation in aerobic scope and respiratory anatomy

Temperature has a profound impact on insect fitness and performance via metabolic, enzymatic or chemical reaction rate effects. However, oxygen availability can interact with these thermal responses in complex and often poorly understood ways, especially in hypoxia-adapted species. Here we test the hypothesis that thermal limits are reduced under low oxygen availability - such as might happen when key life-stages reside within plants - but also extend this test to attempt to explain that the magnitude of the effect of hypoxia depends on variation in key respiration-related parameters such as aerobic scope and respiratory morphology. Using two life-stages of a xylophagous cerambycid beetle, Cacosceles (Zelogenes) newmannii we assessed oxygen-limitation effects on metabolic performance and thermal limits. We complement these physiological assessments with high-resolution 3D (micro-computed tomography scan) morphometry in both life-stages. Results showed that although larvae and adults have similar critical thermal maxima (CTmax) under normoxia, hypoxia reduces metabolic rate in adults to a greater extent than it does in larvae, thus reducing aerobic scope in the former far more markedly. In separate experiments, we also show that adults defend a tracheal oxygen (critical) setpoint more consistently than do larvae, indicated by switching between discontinuous gas exchange cycles (DGC) and continuous respiratory patterns under experimentally manipulated oxygen levels. These effects can be explained by the fact that the volume of respiratory anatomy is positively correlated with body mass in adults but is apparently size-invariant in larvae. Thus, the two life-stages of C. newmannii display key differences in respiratory structure and function that can explain the magnitude of the effect of hypoxia on upper thermal limits

Markerless monocular tracking system for guided external eye surgery

This paper presents a novel markerless monocular tracking system aimed at guiding ophthalmologists during external eye surgery. This new tracking system performs a very accurate tracking of the eye by detecting invariant points using only textures that are present in the sclera, i.e., without using traditional features like the pupil and/or cornea reflections, which remain partially or totally occluded in most surgeries. Two known algorithms that compute invariant points and correspondences between pairs of images were implemented in our system: Scalable Invariant Feature Transforms (SIFT) and Speed Up Robust Features (SURF). The results of experiments performed on phantom eyes show that, with either algorithm, the developed system tracks a sphere at a 360◦ rotation angle with an error that is lower than 0.5%. Some experiments have also been carried out on images of real eyes showing promising behavior of the system in the presence of blood or surgical instruments during real eye surgery. © 2014 Elsevier Ltd. All rights reserved.Monserrat Aranda, C.; Rupérez Moreno, MJ.; Alcañiz Raya, ML.; Mataix, J. (2014). Markerless monocular tracking system for guided external eye surgery. Computerized Medical Imaging and Graphics. 38(8):785-792. doi:10.1016/j.compmedimag.2014.08.001S78579238