1,721,054 research outputs found
Modal analysis of a fan assembly aimed to active noise control in a wind tunnel
No full textThe paper describes the modal analysis of the axial fan, powering one of the wind tunnel of the Department of Aeronautical Engineering of the University of Naples. Starting form the basic components, a numerical finite element model has been assembled. Whenever possible, all the numerical information have been continuously cross-checked with the ongoing experimental analysis. In particular it has been used also the modal density as further parameter, in order to tune the finite element model at growing excitation frequencies. The experimental modal analysis has been carried out by using 194 acquisition points and an electrodynamic shaker. The data have been gathered in the modal analysis software, for studying the system in the 0-500 Hz frequency range. The main result of this phase of the work is represented by the identification of the points to excite the structure for obtaining an adequate vibration and noise reduction through an active device. Looking at this next phase, noise measurements have been also carried out. The preliminary obtained result by the presented experiences have demonstrated that an active noise control device acting on the axial fan could be designed for the wind tunnel facility
Numerical evaluation and experimental comparison of airframe noise for the optimization of next generation aircraft design
No full textIn this paper the airframe noise of civil transport aircraft is numerically evaluated and compared with measurements taken in some european airports with the target of separating the airframe contribution from other noise contributions effective on a typical aircraft. The attention has been focused on airframe noise since it sets a lower limit below whichever reduction of noise generated by engine have no significant effect on the overall noise level perceived by an observer and due to the aircraft flyover. The intensity of airframe noise depends on the aircraft configuration: during the cruise the aircraft exhibit an aerodynamically 'clean' configuration that produces less noise than the configuration assumed by the aircraft during landing and take-off, that usually is referred as 'dirty' one. The configuration with slats extended, flaps down and undercarriage lowered is more noisy than the clean configuration. In this paper the results of numerical simulations performed on common operating aircraft are presented: these simulations allow the contribution breakdown and, therefore, the classification of the most noisy airframe components for the different approach and take-off configurations
Interior active noise control in turbofan aircraft: Numerical simulation and optimal actuators positioning using dedicated genetic algorithms
No full textThis paper presents the activities developed by the authors within the first year of the research project named M.E.S.E.M.A. (Magnetoelastic Energy Systems for Even More Electric Aircraft) funded by the European Commission within the 6th Framework Program and coordinated by the "Dipartimento di Progettazione Aeronautica" of the University of Naples "Federico II" (DPA). One of the main targets for the MESEMA Consortium consists in reducing the level of disturbance noise in turbofan aircraft. A noise & vibration control system using magnetostrictive actuators will be designed, developed and tested, with the goal of controlling noise & vibrations in a frequency range between 150-500 Hz. The environmental noise & vibration excitations will be representative of a small/medium turbofan aircraft case. During the first two years of the project a numerical (Finite Element) model of the test article has been developed in MSC/NASTRAN environment coupling the structural part with the interior acoustic volume. Furthermore a complete experimental characterisation of the test-article has been carried on. Numerical model has been correlated with experimental results, updating it in order to achieve the best fitting in terms of natural frequencies and modes shapes at low frequencies [1], Then the updated model has been employed to derive the required control actuators performances in order to achieve the best theoretical interior noise control predicted using a well consolidated "feed- forward" approach [2] and Genetic Algorithms have been employed in order to optimise the positioning of the actuators
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
Experimental modal analysis of the Garigliano cable-stayed bridge
No full textAn experimental study was carried out on the Garigliano Cable-Stayed Bridge (Italy) order to find out its dynamic characteristics, such as resonance frequencies, modal shapes and damping factors. Measurements were done by using a limited number of sensors, properly located on the structure. This was excited by means of a lorry driving over a wooden bar. The experimental results were compared with those obtained from a finite element analysis. The numerical model, defined by means of the experimental dynamic analysis, was also used for the structural analysis under service loads as part of structural testing
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
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