1,720,996 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
[Deux expositions] "Chine moderne : l'architecture depuis 1949" et "Métropoles en miroir" - énsa de Paris-Belleville - 18 juin au 19 juillet 2024
No full textDeux expositions ont été inaugurées hier mardi 25 juin 2024 à 17h30 à l'école nationale supérieure d'architecture de Paris-Belleville : "Chine moderne : l'architecture depuis 1949" "Métropoles en miroir" Chine moderne : l'architecture depuis 1949 Commissaire : Li Xiangning - Concernant l’exposition à l’ENSA Paris-Belleville :Co-commissaires : Mete Kutlu & Cristiana MazzoniCommissaires adjoints : Mo Wanli, Wang Xuerui Équipe de commissariat : Mao Jianyuan, Li Wenyuan Conception de l’expositio..
Modelling, Control, and Handling Quality Analysis of the Flying-V
No full textOver the last five decades, the majority of commercial aircraft consisted of the traditional tube-and-wing configuration. This traditional configuration is approaching a fuel efficiency asymptote. Besides that, with the increasing number of passengers and cargo transported by air every year, and environmental impact as an important factor in aircraft design, there is a necessity for a solution that is able to boost aircraft efficiency. Currently, the faculty of Aerospace Engineering at TU Delft is working on a promising aircraft configuration, namely the Flying-V. This is a specific type of flying wing that is tailless, V-shaped, and consists of two cylindrical pressurised cabins located in the leading edge of the wing. Wind tunnel experiments show that the aircraft is longitudinally statically stable up to an angle of attack of 20¶, after that pitch break occurs. Besides that, research performed on the aerodynamic coefficients obtained using the Vortex Lattice Method and results from the maiden flight test of a scale model of the aircraft conclude that the Dutch roll mode is unstable. Therefore, this research defines a set of key stability and handling quality requirements based on civil aviation authorities combined with military standards for cruise- and approach conditions. These key requirements are consequently assessed with a simulation model of the aircraft using aerodynamic coefficients obtained from the Vortex Lattice Method and wind tunnel experiments. In an attempt to make the key stability and handling quality characteristics of the TU Delft Flying-V adhere to the defined requirements, this thesis aims to contribute to this research field by designing a nonlinear Incremental Nonlinear Dynamic Inversion (INDI) flight control system that is applied to the simulation model of the aircraft. Finally, the performance of the aircraft using this flight control system is assessed and proposals for aerodynamic design changes and control layout design changes are given.Aerospace Engineerin
Variations on the Author
Full text link“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
Full text linkWe 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
Online Black-box Shape Optimization for a Seamless Active Morphing Wing
No full textRecent trends in aviation highlight the ever-increasing need for fuel economy and sustainability. Active morphing technology can offer significant benefits over conventional wing designs. Inspired by nature, smart morphing technologies enable the aircraft of tomorrow to sense their environment and adapt the shape of their wings in-flight to minimize fuel consumption and emissions. A primary challenge on the road to this future is the question of how to use the knowledge gathered from sensory data to establish an optimal shapeadaptively and continuously in-flight.To address this challenge, this thesis proposes a novel architecture for online black-box aerodynamic performance optimization for active morphing wings. The proposed method seeks to extend the scope of state-of-the-art online performance optimization methods by integrating a global online-learned radial basis function neural network model with a derivative-free evolutionary optimization strategy. The effectiveness of the optimization strategy was tested on a Vortex Lattice Method aerodynamic model of an over-actuated morphing wing that was corrected using previously collected wind tunnel data. Simulations show that the proposed method is able to control the morphing shape and angle of attack to achieve various target lift coefficients with better aerodynamic efficiency than the unmorphed wing shape. Furthermore, the effectiveness of the optimization architecture was experimentally evaluated on an active trailing-edge camber morphing wing demonstrator with distributed sensing and control, the SmartX-Alpha, in the open jet facility of Delft University of Technology. Compared to the unmorphed shape, a 7.8 % drag reduction was realized, while achieving the required amount of lift. Further data-driven predictions have indicated that even higher reductions in drag are achievable and have provided insight into the trends in optimal wing shapes for a wide range of lift targets.Aerospace Engineerin
Active Fault-Tolerant Incremental Sliding-Mode Flight Control Against Control Reversal
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Aerospace Structures & Computational Mechanic
Incremental Sliding Mode Control for Aeroelastic Launch Vehicles with Propellant Slosh
No full textThis paper focuses on the attitude control and propellant slosh suppression of aeroelastic launch vehicles. Four candidate controllers are proposed: the Linear Quadratic Regulator (LQR), the Incremental Non-linear Dynamic Inversion (INDI) control, the Incremental Sliding Mode Control (INDI-SMC), and the Feedback Linearisation-based Sliding Mode Control (FL-SMC). Theoretical analyses show INDI itself is unable to deal with under-actuated systems. Therefore, when applied to the launch vehicle directly, it cannot simultaneously track the pitch command and effectively suppress the slosh dynamics. This issue is solved by INDI-SMC, which also has enhanced robustness against both matched and unmatched uncertainties. Furthermore, despite its reduced model dependency, INDI-SMC has better robustness against model uncertainties and external disturbances than FL-SMC. These merits of INDI-SMC are verified by various simulation results. First, when the nominal plant configuration is adopted, the system using INDI-SMC has the smallest pitch-angle tracking error. The slosh motion is also effectively damped out. Second, Monte-Carlo studies are used to test the robustness of LQR, INDI-SMC, and FL-SMC to parametric uncertainties. Among these three controllers, LQR shows the worst performance and largest control-effort outliers. On the contrary, both INDI-SMC and FL-SMC can resist a wider range of perturbations without significant performance degradation. Even so, the tracking and slosh damping performance of INDI-SMC is still the best. Finally, both INDI-SMC and FL-SMC show robustness against unmodeled dynamics, while the robust performance of INDI-SMC is superior.Virtual/online event due to COVID-19Astrodynamics & Space MissionsAerospace Structures & Computational Mechanic
Nonlinear Robust Control and Observation for Aeroelastic Launch Vehicles with Propellant Slosh in a Turbulent Atmosphere
No full textThis paper focuses on the attitude control and propellant slosh suppression of aeroelastic launch vehicles in a turbulent atmosphere. For a five-degree pitch-angle block command, the tracking performance of the selected Incremental Non-Linear Dynamic Inversion Sliding Mode Controller (INDI-SMC) shows excellent tracking performance. However, turbulence still inevitably leads to oscillatory behaviour in the swivel command. Various filter designs have been implemented to improve the smoothness of INDI-SMC. Using either a notch or band-pass filter in the sensor-feedback loops of pitch angle and pitch rate only marginally reduced the swivel oscillations, but did not solve the problem for the rigid-body control. For the flexible launcher with slosh dynamics, filtering of the sensor-feedback signals reduced the oscillations in swivel command, and elastic and slosh motion significantly, but could not completely remove them. The preliminary design of a rigid-body state observer has been included, and the results show that the INDI-SMC controller remains stable in the presence of engine dynamics, sloshing, flexible modes, input errors due to the use of rigid-body and slosh-state observers, while flying in a turbulent wind field
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