1,721,417 research outputs found
II. Documents relatifs aux traitements des professeurs de l'ancienne université de Louvain, vers 1609
No full textHermans C. R. II. Documents relatifs aux traitements des professeurs de l'ancienne université de Louvain, vers 1609. In: Compte-rendu des séances de la commission royale d'histoire. Deuxième Série, Tome 5, 1853. pp. 405-415
Hoe denken schoolleiders over de pedagogische vormgeving van hun school
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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
Rotorcraft-pilot couplings: Analysis and detection in a safety enhancement framework
No full textNowadays, the complexity of high speed civil transport and highly-augmented rotorcraft, has led to an increase in the chances of encountering unwanted unstable phenomena, such as the so called Aircraft/Rotorcraft-Pilot Couplings (A/RPCs) or Pilot-Induced Oscillations (PIOs), whose unpredictability has given rise to a serious problem concerning the safety of a mission. When talking about PIOs, McRuer de- 1ned them as “inadvertent, sustained aircraft oscillations which are a consequence of an abnormal joint enterprise between the aircraft and the pilot”. However, A/RPCs, these undesirable events associated with the interaction between pilot and aircraft, have become diverse and more complex than those encountered in the past. At the moment, there are different methods available to prevent and detect Cat. I/II A/RPC, but particular interest has recently arisen in this topic for 2ight simulation applications as any enhancement of these tools in order to accurately and objectively predict, detect (in real-time) and alleviate RPCs will be greatly welcomed. One of the main questions to be answered through the efforts carried out within this work is related to the better detection in real-time of embedded tendencies to RPCs in modern aircraft. To answer this question, initially an assessment of the eZcacy of the Phase-Aggression Criterion (PAC), which has been designed a few years ago at the University of Liverpool, will be undertaken either: as a means of alerting the pilot to conditions likely to lead to the onset of a PIO; or, given that the time available for the pilot to counteract may be extremely limited, as a means to assist him/her in alleviating (automatically) the PIO condition itself. Preliminary results from 2ight simulation trials to explore how best to achieve this will be reported. Moreover, this work will report on the development of PAC boundaries for more highly augmented response types. Furthermore, as classi1ed by McRuer, Cat. III PIO, which is nonlinear in essence, is the most complex one. However, the researches on Cat. III PIO are rare. This paper will reveal some elementary results of Cat. III PIO. Since there is no existing method used for predicting and detecting Cat. III PIO, this paper utilized the characteristics of PIO, such as the amplitude, the oscillation frequency and ultimate tendency of key aircraft response states to judge Cat. III PIO preliminarily. By using this elementary judgment of PIO, we studied the following factors: time delay of pilot input and helicopter main body, actuator position saturation, actuator rate limit and SCAS control authority in triggering PIO. Results show that PIO induced by actuator position saturation, actuator rate limit and SCAS control authority can be regarded as Cat. III PIO as the variation of these factors can be viewed as a kind of transition of effective controlled vehicle dynamics. These kinds of transition can cause a mismatch between the effective controlled vehicle dynamics and pilot control strategy, which is the main cause of Cat. III PIO. Copyright Statement The authors con1rm that they, and/or their company or organization, hold copyright on all of the original material included in this paper. The authors also con1rm that they have obtained permission, from the copyright holder of any third party material included in this paper, to publish it as part of their paper. The authors con1rm that they give permission, or have obtained permission from the copyright holder of this paper, for the publication and distribution of this paper as part of the ERF proceedings or as individual offprints from the proceedings and for inclusion in a freely accessible web-based repository.Control & Simulatio
Hoplite - a conceptual design environment for helicopters incorporating morphing rotor technology
No full textThe SABRE project has been initiated under the EU’s Horizon 2020 programme for development of blade morphing technologies for helicopter rotors. The project targets reductions in fuel burn and NOx emissions of upto 5-10% through the use of morphing rotor blades. A new design tool for rotorcraft, HOPLITE, is being developed to investigate the effects of rotor morphing on engine emissions and fuel burn. HOPLITE uses low-fidelity models for quick and reasonably accurate force and power calculations for major components of the vehicle. The main rotor is modelled using the Blade Element Method, and accounts for changes in blade shape due to rotor morphing and other geometrical modifications. Additionally, a robust fuselage parameterization method, and an equation based engine model have been incorporated in HOPLITE to include the impact of rotor morphing on the design of the helicopter as a whole. The main argument behind the development of HOPLITE is to combine various low-fidelity methods, such that quick design assessments can be performed for various purposes, and, simultaneously, have sufficient fidelity to capture changes in blade shape due to rotor morphing. Actuator disk models can perform a quick analysis, but are unable to match the required level of fidelity. In comparison, traditional CFD simulations or experimental campaigns will be cost and time intensive. Hence, there is a need for a new tool. Due to a multidisciplinary and modular approach used by HOPLITE, it can be used for a wide range of tasks, such as design space exploration and optimization. Furthermore, it can be used in conjuction with high fidelity methods. This paper describes the current work done towards the development of various modules of the tool, theoretical aspects of engine, fuselage and rotor modelling, and initial results obtained during development and testing of individual modules. Theoretical aspects of conceptual design capabilities of the tool have also been briefly described in this paper. Future work will involve development and integration of conceptual design functions in HOPLITE for conventional helicopters, and expansion of these algorithms to non-conventional rotorcraft designs.Flight Performance and PropulsionControl & Simulatio
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
Wind turbine wakes and helicopter operations: An overview of the garteur HC-AG23 activities
Full text linkThe effects of a wind turbine wake on General Aviation and the behaviour of helicopters in the tip vortex of large fixed-wing aircraft has been topic of research in the past years, but less is known about the interactions of helicopters operating in a wind turbine wake. A dedicated GARTEUR Action Group, HC-AG23, consisting of European universities and research institutes was formed to investigate helicopter behaviour in a wind turbine wake and to study the consequences for helicopter handling and safety of flight. The activities are structured in work packages addressing wind turbine wake identification, wake experiments and computations, offline and piloted simulations and management and dissemination activities. This paper presents an overview of the partners' activities and provides a short overview of the results that have been achieved in the past three years
Eigenmode Distortion as a Novel Criterion for Motion Cueing Fidelity in Rotorcraft Flight Simulation
No full textEigenmode distortion (EMD) is a novel methodology developed to study the degradation of perceived vehicle dynamics as a result of motion cueing algorithms (MCA’s) applied in rotorcraft 2ight simulators. This paper brie2y introduces EMD and subsequently describes its application in a pilot-in-the-loop experiment conducted on the SIMONA Research Simulator at Delft University of Technology. The experiment considers a precision hover task performed by two test pilots in three different motion cueing conditions. Each of the evaluated conditions is devised such to best reproduce one of the vehicle modes (pitch/heave subsidences and phugoid) simulated using an independently developed, three degree-of-freedom, longitudinal, nonlinear model of the AH-†„ Apache helicopter. The experiment yielded a number of interesting results. For example, the mode participation factors (MPFs) computed using recorded model states showed that the unstable phugoid mode dominates the overall dynamic response in all conditions evaluated. Also, based on the relative distribution of MPF’s across the three motion conditions, some indication of a change in pilot control behaviour as a result of motion cues (or lack thereof) was exposed. Finally, subjective pilot ratings suggest that the motion cueing condition optimized for the pitch subsidence mode is preferred, even though this is not the dominant mode in the vehicle’s response. The condition corresponding to the heave subsidence mode (i.e., only vertical motion cues) is appreciated least.Control & SimulationControl & Operation
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
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