1,721,341 research outputs found
Special issue MEDYNA 2020
No full textMechanical systems such as vehicle suspensions, robot manipulators, and spacecraft are often required to operate with high performances and shock and vibrations, which may quickly cause unacceptable system states, are perceived as the most important problems in mechanical system design. The development of methods for vibro-acoustic characterization and control has become an important topic of research and several methods, with analytical, numerical and experimental approaches, have been proposed to identify the vibro-acoustic and impact characteristics of different types of structure belonging to different engineering fields.
This Special Issue of Journal of Mechanical Engineering Science (JMES) contains selected, extended and peer-reviewed papers that were initially presented at the 3rd in the series Euro-Mediterranean Conference on Structural Dynamics and Vibroacoustics (MEDYNA 2020) in Napoli, Italy, from February 17th to February 19th, 2020 (https://medyna2020.sciencesconf.org/). The emphasis of the conference series is on methods, techniques and technologies – under theoretical, numerical and experimental approaches – in acoustics, vibration, impacts and structural health monitoring and the present Special Issue highlights the current state-of-the-art of this fields and innovative ideas applied in several engineering applications, such as: aeronautics, automotive, building, etcetera
Sensitivity analysis for the parameter identification of a PEM fuel cell
No full textThis paper discusses a sensitivity analysis for circuit model identification of fuel cell in Electrochemical Impedance Spectroscopy (EIS) experiments. The analysis is aimed at evaluating the impact of the aggregation of electric parameters on the identification performance, in the presence of sinusoidal input currents. The result of this analysis is validated in a numerical experiment, where a dual-extended Kalman filter estimates both fuel cell state and parameters in the presence of a typical EIS stimulus, that consists of a sequence of sinusoidal signal at various frequencies
Series and parallel coupling of 3D printed micro-perforated panels and coiled quarter wavelength tubes
No full textMicro-perforated panel sound absorbers are widely used in noise control applications in the fields of architectural acoustics and transport acoustics. Combining micro-perforated panels with other resonant or sound absorbing systems may broaden the frequency range in which they absorb sound while ensuring that large sound absorption values are reached. In this work, a hybrid sound absorber that combines a micro-perforated panel and a coiled quarter wavelength tube is proposed. Series and parallel configurations of these two systems are studied from analytical, numerical, and experimental point of views. A comparison of two three-dimensional (3D) printing techniques for the production of samples highlights the main challenges for the practical implementation of the proposed design. The advantages and limitations of series and parallel arrangements are discussed and while the parallel configuration is more complex to setup in practice, it provides an improved sound-absorbing performance compared with the series configuration. Finally, the reproducibility of the hybrid absorber in parallel configuration is confirmed by testing samples that were produced with two different 3D printers and in two different laboratories
Optimization under Uncertainty using Adjoint Solutions and Radial Basis Function based Morphing
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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
Early Detection of Photovoltaic Panel Degradation through Artificial Neural Network
No full textIn this paper, an artificial neural network (ANN) is used for isolating faults and degradation phenomena occurring in photovoltaic (PV) panels. In the literature, it is well known that the values of the single diode model (SDM) associated to the PV source are strictly related to degradation phenomena and their variation is an indicator of panel degradation. On the other hand, the values of parameters that allow to identify the degraded conditions are not known a priori because they can be different from panel to panel and are strongly dependent on environmental conditions, PV technology and the manufacturing process. For these reasons, to correctly detect the presence of degradation, the effect of environmental conditions and fabrication processes must be properly filtered out. The approach proposed in this paper exploits the intrinsic capability of ANN to map in its architecture two effects: (1) the non-linear relations existing among the SDM parameters and the environmental conditions, and (2) the effect of the degradation phenomena on the I−V curves and, consequently, on the SDM parameters. The ANN architecture is composed of two stages that are trained separately: one for predicting the SDM parameters under the hypothesis of healthy operation and the other one for degraded condition. The variation of each parameter, calculated as the difference of the output of the two ANN stages, will give a direct identification of the type of degradation that is occurring on the PV panel. The method was initially tested by using the experimental I−V curves provided by the NREL database, where the degradation was introduced artificially, later tested by using some degraded experimental I−V curves.Photovoltaic Materials and Device
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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