1,720,961 research outputs found
Design and optimization of modular lattice structures for aerospace applications
No full textDans l'industrie aérospatiale, il existe une demande continue pour des aérostructures plus légères, motivée par la nécessité d'améliorer l'efficacité énergétique et les performances globales de l'avion. Par conséquent, le secteur aérospatial connaît actuellement deux changements majeurs : l'adoption d'avions à hydrogène et électriques, visant à développer des technologies aéronautiques plus propres et durables. Ces évolutions offrent des opportunités pour explorer des concepts innovants tels que l'aile volante ou les ailes haubanées transsoniques, s'éloignant de la configuration traditionnelle tube-et-aile. Une approche prometteuse pour répondre à ces demandes est l'utilisation de structures modulaires en treillis, reconnues pour leurs propriétés ultralégères et leur modularité. La conception modulaire offre divers avantages, notamment l'assemblage de grandes structures à partir de modules répétitifs plus petits, faciles à fabriquer, la réparabilité sur le terrain et l'assemblage rapide pour des structures temporaires.L'objectif de cette thèse est de développer une méthodologie de conception et d'optimisation pour des aérostructures ultralégères et modulaires. Initialement, nous avons réalisé une revue de la littérature existante pour identifier la base algorithmique la plus adaptée à l'optimisation de structures monolithiques (non modulaires). Après une comparaison approfondie, nous avons sélectionné l'approche nommé Truss Topology Optimization (TTO), qui utilise des barres comme élément de discrétisation de la structure. Cependant, la formulation classique du TTO présente des limitations, telles que l'incapacité à traiter les contraintes de flambage, à prendre en compte plusieurs cas de charge, à limiter l'élancement minimum et à assurer la compatibilité mécanique. Pour surmonter ces défis, nous avons formulé une approche globale et développé un algorithme innovant d'optimisation en deux étapes. Cela implique d'utiliser un problème simplifié pour générer une solution initiale, qui sert de point de départ pour l'optimisation à l'aide d'une formulation complète.La deuxième partie de la thèse se concentre sur l'adaptation de la formulation monolithique proposée pour modéliser des structures modulaires. Initialement, nous nous concentrons sur l'optimisation de la topologie d'une structure entièrement modulaire, où un seul module est répété tout au long du design. Nous examinons comment les hyperparamètres, tels que le nombre de sous-domaines et la complexité des modules, affectent les performances mécaniques de la structure. Ensuite, nous explorons un scénario plus complexe en optimisant plusieurs topologies de modules et leur disposition dans la structure. Cela est réalisé grâce à une nouvelle stratégie de résolution basée sur une approche Discrete Material Optimization (DMO), utilisant un optimiseur à descente de gradient.En abordant les défis de la conception légère et de la modularité dans les aérostructures, cette recherche vise à contribuer à l'évolution continue des technologies aérospatiales et à améliorer l'efficacité et les performances des futurs avions.In the aerospace industry, there is a continuous demand for lighter aerostructures driven by the need to improve fuel efficiency and overall performance. Consequently, the aerospace sector is undergoing two significant shifts: the adoption of hydrogen-powered and electric planes, aimed at developing cleaner and more sustainable aviation technologies. These changes present opportunities to explore innovative concepts such as the flying wing or transonic dry truss-braced wings, deviating from the traditional tube-and-wing configuration. One promising approach to meet these demands is the utilization of modular lattice structures, known for their ultralight properties and modularity. Modular designs offer various advantages, including the assembly of large structures from smaller, easily manufacturable repeating modules, on-field repairability, and rapid assembly for temporary structures.The objective of this thesis is to develop a design and optimization methodology for ultralight and modular aerostructures. Initially, we conducted a review of existing literature to identify the most suitable algorithm basis for optimizing monolithic (non-modular) structures. After a comprehensive comparison, we selected the Truss Topology Optimization (TTO) approach, which utilizes bars as the discretizing element of the structure. However, the classic TTO formulation has limitations, such as the inability to address buckling constraints, consider multiple load cases, limit the minimum slenderness, and ensure mechanical compatibility. To overcome these challenges, we formulated a comprehensive approach and developed an innovative two-step optimization algorithm. This involves using a relaxed problem to generate an initial solution, which serves as the starting point for optimization using a complete formulation.The second part of the thesis focuses on adapting the proposed monolithic formulation to model modular structures. Initially, we concentrate on optimizing the topology of a fully modular structure, where a single module is repeated throughout the design. We investigate how hyperparameters, such as the number of subdomains and module complexity, affect the mechanical performance of the structure. Subsequently, we explore a more complex scenario by optimizing multiple module topologies and their layout within the structure. This is achieved through a newly proposed solving strategy based on a modified Discrete Material Optimization (DMO) approach, employing a gradient-based optimizer.By addressing the challenges of lightweight design and modularity in aerostructures, this research aims to contribute to the ongoing evolution of aerospace technologies and advance the efficiency and performance of future aircraft
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Conception et optimisation de structures lattice modulaires pour des applications aérospatiales
No full textIn the aerospace industry, there is a continuous demand for lighter aerostructures driven by the need to improve fuel efficiency and overall performance. Consequently, the aerospace sector is undergoing two significant shifts: the adoption of hydrogen-powered and electric planes, aimed at developing cleaner and more sustainable aviation technologies. These changes present opportunities to explore innovative concepts such as the flying wing or transonic dry truss-braced wings, deviating from the traditional tube-and-wing configuration. One promising approach to meet these demands is the utilization of modular lattice structures, known for their ultralight properties and modularity. Modular designs offer various advantages, including the assembly of large structures from smaller, easily manufacturable repeating modules, on-field repairability, and rapid assembly for temporary structures.The objective of this thesis is to develop a design and optimization methodology for ultralight and modular aerostructures. Initially, we conducted a review of existing literature to identify the most suitable algorithm basis for optimizing monolithic (non-modular) structures. After a comprehensive comparison, we selected the Truss Topology Optimization (TTO) approach, which utilizes bars as the discretizing element of the structure. However, the classic TTO formulation has limitations, such as the inability to address buckling constraints, consider multiple load cases, limit the minimum slenderness, and ensure mechanical compatibility. To overcome these challenges, we formulated a comprehensive approach and developed an innovative two-step optimization algorithm. This involves using a relaxed problem to generate an initial solution, which serves as the starting point for optimization using a complete formulation.The second part of the thesis focuses on adapting the proposed monolithic formulation to model modular structures. Initially, we concentrate on optimizing the topology of a fully modular structure, where a single module is repeated throughout the design. We investigate how hyperparameters, such as the number of subdomains and module complexity, affect the mechanical performance of the structure. Subsequently, we explore a more complex scenario by optimizing multiple module topologies and their layout within the structure. This is achieved through a newly proposed solving strategy based on a modified Discrete Material Optimization (DMO) approach, employing a gradient-based optimizer.By addressing the challenges of lightweight design and modularity in aerostructures, this research aims to contribute to the ongoing evolution of aerospace technologies and advance the efficiency and performance of future aircraft.Dans l'industrie aérospatiale, il existe une demande continue pour des aérostructures plus légères, motivée par la nécessité d'améliorer l'efficacité énergétique et les performances globales de l'avion. Par conséquent, le secteur aérospatial connaît actuellement deux changements majeurs : l'adoption d'avions à hydrogène et électriques, visant à développer des technologies aéronautiques plus propres et durables. Ces évolutions offrent des opportunités pour explorer des concepts innovants tels que l'aile volante ou les ailes haubanées transsoniques, s'éloignant de la configuration traditionnelle tube-et-aile. Une approche prometteuse pour répondre à ces demandes est l'utilisation de structures modulaires en treillis, reconnues pour leurs propriétés ultralégères et leur modularité. La conception modulaire offre divers avantages, notamment l'assemblage de grandes structures à partir de modules répétitifs plus petits, faciles à fabriquer, la réparabilité sur le terrain et l'assemblage rapide pour des structures temporaires.L'objectif de cette thèse est de développer une méthodologie de conception et d'optimisation pour des aérostructures ultralégères et modulaires. Initialement, nous avons réalisé une revue de la littérature existante pour identifier la base algorithmique la plus adaptée à l'optimisation de structures monolithiques (non modulaires). Après une comparaison approfondie, nous avons sélectionné l'approche nommé Truss Topology Optimization (TTO), qui utilise des barres comme élément de discrétisation de la structure. Cependant, la formulation classique du TTO présente des limitations, telles que l'incapacité à traiter les contraintes de flambage, à prendre en compte plusieurs cas de charge, à limiter l'élancement minimum et à assurer la compatibilité mécanique. Pour surmonter ces défis, nous avons formulé une approche globale et développé un algorithme innovant d'optimisation en deux étapes. Cela implique d'utiliser un problème simplifié pour générer une solution initiale, qui sert de point de départ pour l'optimisation à l'aide d'une formulation complète.La deuxième partie de la thèse se concentre sur l'adaptation de la formulation monolithique proposée pour modéliser des structures modulaires. Initialement, nous nous concentrons sur l'optimisation de la topologie d'une structure entièrement modulaire, où un seul module est répété tout au long du design. Nous examinons comment les hyperparamètres, tels que le nombre de sous-domaines et la complexité des modules, affectent les performances mécaniques de la structure. Ensuite, nous explorons un scénario plus complexe en optimisant plusieurs topologies de modules et leur disposition dans la structure. Cela est réalisé grâce à une nouvelle stratégie de résolution basée sur une approche Discrete Material Optimization (DMO), utilisant un optimiseur à descente de gradient.En abordant les défis de la conception légère et de la modularité dans les aérostructures, cette recherche vise à contribuer à l'évolution continue des technologies aérospatiales et à améliorer l'efficacité et les performances des futurs avions
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
