1,720,963 research outputs found
Experimental validation of novel friction damper for anti-seismic control of civil structures
No full textThis work presents a new semi-active friction damper device, based on piezoelectric technology, for the anti-seismic
control of civil structures. A civil structure, representative of a two storey steel framed building, and a reference
seismic excitation signal were used to size the semi-active friction damper. Matlab-Simulink based software (EarthSim) was
implemented to simulate the response of the steel frame to the seismic excitation, applied at the base of the structure. The dynamic response was evaluated both in the case of the active device (controlled response) as well as the non-active device. Different configurations (in terms of the device’s overall performance and control algorithm parameters) were simulated for the active control system. In so doing, a reference configuration for the structural control system was determined by identifying optimal values for control logic parameters, as well as for the dampers preload and maximum force.
Focus then turned to the structural design phase. 3D CAD was used to generate a digital mock-up of the device and structural
analyses were conducted using the finite element method.
The proposed device presents an original conceptual layout, characterised by a compact and easy allocation of the piezo-actuator which is installed inside the piston of the damper. A highly efficient transmission chain allows for the transfer of the compression force generated by the piezo-actuator, to four pads of friction material,preventing the motion of the piston along its chamber. Theoretical performances were validated by means of experimental tests carried out on a physical prototype, loaded through a hydraulic test machine
Preliminary theoretical study about a "Piezoelectric Shingle" for a piezoelectric energy harvesting system in presence of rain
No full textThe present work is focused on the proposal of the idea of a "Piezoelectric Shingle" as a new energy harvesting system, based on meteorological precipitations as the rain. It is presented a preliminary analysis about the state of art of energy harvesting systems, based on piezoelectric technology, showing potentiality, limits and other experiences in the field of interest. Besides the paper treats about the main features of rainy phenomena, interesting for an energy harvesting system, reconsidering some theoretical/empirical models. Models are addressed to define the limit velocity of raindrops and a distribution law between dimension of raindrops and the nature of rainfall. After considerations about the annual quantity of water, fallen in a region, the authors propose the ideation of some key patterns for a piezoelectric energy harvesting system from rainy precipitations. Each scheme is analyzed and evaluated for the selection of only one conceptual ide
Preliminary experimental/numerical study of the vibration annoyance control of a windshield wiper mechanical system through a synchronized switch shunt resonator (SSSR) technology
Full text linkThe present work focuses on the study and analysis of vibrations generated by the electrical motor of a wiper system on its support bracket referring to an hatchback vehicle passenger car. In the electric motor of the wiper system there can be present an imbalance transmitting vibrations to the main body via the support bracket. In this paper, after a short resume of available synchronized switch shunt damping methods, a preliminary experimental evaluation of their potential performance on noise control of the wiper system is reported. After preliminary experimental measurements of dynamic vibration by the use of vibrometer laser both on the real hatchback car then in laboratory environment, a numerical model has been created to evaluate deformations of the support bracket for comparison with the experimental data. This work realizes the preliminary numerical/experimental characterization activity to set up a new application of a control system based on a semi-active technique, called Synchronized Switch Shunt Resonator (SSSR)
Multi-body model validation of a landing gear system for a general aviation aircraft
No full textThe present work is aimed to numerically validate the experimental drop test results [1], related to the landing gear of a general aviation aircraft, in order to define an appropriate simulation methodology able to save time, costs and risks due to structural design and experimental test campaign required in the certification phase.
The aircraft selected for this research activity is the AP-68TP-300 Spartacus, an Italian nine-seat, twin-engined, high wing monoplane, realized by Vulcanair S.p.a..
The multi-body approach has been developed through the MSC Adams software, starting from a simplified 1D model up to a more detailed 3D one.
The comparison between numerical and experimental results in terms of load factors has been carried out in accordance with CS-23 [2-3] (Certification Specifications for Normal, Utility, Aerobatic and Commuter Aeroplanes), and it has shown a good correlation, especially for the 3D model, since it better fits the real behavior of the entire system
Multi-Body Approach to the Simulation of particular Drop Test for an Aircrsft Landing Gear
No full textThis work deals with the effectiveness of dynamic analysis for a fixed landing gear, performed through a multi-body software by providing evidence of consistency between numerical simulation and experimental drop test results for the aircraft AP.68 TP-300. After the realization of Digital Mock-up of the main components of landing gear in a C.A.D. 3D, we have imported them in ADAMS environment and we have virtually mounted them to reproduce the real constraints. In ADAMS the model of the test article has been realized too. The fuselage of aircraft and constitutive parts of landing gear have been modeled all as rigid body. Only the leaf spring and tire have been simulated as flexible body. An ADAMS Tire Model has been used in the simulation and information about the ground has been added in a Road Data file. Simulations to reproduce experimental drop test, characterized by defined weights of falling mass and height, have been developed. The results show a good correlation between numerical simulation and experimental test, which provides preliminary evidence of future possible cost reduction through a potential virtual certification of the landing gear new design development. Future development of the present activity will probably be an application of methodology to other cases for a more extensive validation of its predictive power and development of virtual certification procedure
Numerical Modelling of a Piezo Roof Harvesting System: The Right Component Selection
No full textThe present work focuses on a first study for a piezoelectric harvesting system, finalized to the obtaining of electrical energy from the kinetic energy of rainy precipitation, a renewable energy source not really considered until now. The system, after the realization, can be collocated on the roof of an house, configuring a “Piezo Roof Harvesting System”. After presenting a state of art of the harvesting systems fromenvironmentalenergy,linkedtovibrations,usingpiezoelectricstructures,andof piezoelectricharvestingsystemsfunctioningwithrain,theauthorsproposeananalysis ofthefundamentalfeaturesofrainyprecipitationsforthedefinitionoftheharvesting system.Then,fourkeypatternsfortherealizationofapiezoelectricenergyharvesting systemarediscussedandanalysed,arrivingtothechoiceofacantileverbeamscheme, in which the piezoelectric material works in 31 mode. An electro-mechanical model forthesimulationofperformanceoftheunitfortheenergeticconversion,composed ofthreeblocks,isproposed.Themodelisusedforasimulationcampaigntoperform thefinalchoiceofthemoresuitablepiezoelectricunit,availableonthemarket,which willbeadoptedfortherealizationofthe“PiezoRoofHarvestingSystem”
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
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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