1,721,120 research outputs found
Densità di popolazione e biometria di Corbicula fluminea (Mueller, 1774), bivalve alloctono invasivo nel fiume Ticino (Pavia)
No full textDefinizione dello smorzamento equivalente per strutture in muratura a supporto della progettazione agli spostamenti
No full textNegli ultimi anni diversi studi hanno dimostrato l’importanza di correlare gli stati limite di progetto a livelli di prestazione definiti dallo spostamento, al fine di ottenere un migliore controllo sul danno atteso in seguito ad un evento sismico.
Gli spettri in spostamento proposti dalla normativa per valori dello smorzamento superiori al valore convenzionale del 5% sono generalmente ottenuti, come per l’Eurocodice 8 e le Norme Tecniche del 2008, applicando un fattore di riduzione agli spettri elastici smorzati del 5%. Tale fattore viene definito in funzione dello smorzamento viscoso equivalente, che dipende dalla dissipazione di energia per isteresi.
In questo lavoro viene presentata una procedura per la determinazione dello smorzamento isteretico per strutture in muratura. Nella procedura si fa ricorso al sistema lineare equivalente, il cui periodo di oscillazione viene determinato attraverso analisi dinamiche non lineari su sistemi idealizzati ad un grado di libertà, utilizzando accelerogrammi sintetici spettro-compatibili. Le analisi sono state condotte utilizzando un modello isteretico tarato sui risultati sperimentali ottenuti da prove cicliche di compressione e taglio effettuate presso l'Università di Padova
Definition of equivalent damping for masonry structures in support of displacement based design
No full textIn the last years, several researches have established the importance to correlate design limit states to performance levels defined by displacement, in order to obtain a better control on expected damage after an earthquake.
The displacement spectra proposed by code for damping values higher than the nominal value of 5% of critical are generally obtained, as in the case of Eurocode 8 and the Italian Technical Code (2008), by applying a scaling factor to the elastic response spectras 5% damped. This factor is defined as a function of equivalent viscous damping, which depends on hysteretic energy dissipation.
The paper presents a procedure for determining the hysteretic damping for reinforced masonry structures. The method makes use of the equivalent linear system, whose vibration period is determined by nonlinear dynamic analysis on single degree of freedom idealized system, by using synthetic spectrum compatible time histories. The analyses are performed using an hysteretic model calibrated on experimental results obtained from cyclic shear compression tests that were carried out by the University of Padova
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
Investigation on Reference Frames and Time Systems in Multi-GNSS
Full text linkReceivers able to track satellites belonging to different GNSSs (Global Navigation Satellite Systems) are available on the market. To compute coordinates and velocities it is necessary to identify all the elements that contribute to interoperability of the different GNSSs. For example the timescales kept by different GNSSs have to be aligned. Receiver-specific biases, or firmware-dependent biases, need to be calibrated. The reference frame used in the representation of the orbits must be unique. In this paper we address the interoperability issues from the standpoint of a Single Point Positioning (SPP) user, i.e., using pseudoranges and broadcast ephemeris. The biases between GNSSs timescales and receiver-dependent biases are analyzed for a set of 31 MGEX (Multi-GNSS Experiment) stations over a time span of more than three years. Time series of biases between timescales of GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), Galileo, BeiDou, QZSS (Quasi-Zenith Satellite System), SBAS (Satellite Based Augmentation System) and NAVIC (Navigation with Indian Constellation) are investigated, in addition to the identification of events like discontinuity of receiver-dependent biases due to firmware updating. The GPS broadcast reference frame is shown to be aligned to the one (IGS14) realized by the precise ephemeris of CODE (Center for Orbit Determination in Europe) to within 0.1 m and 2 milliarcsec, with values dependent on whether IIR-A, IIR-B/M or IIF satellite blocks are considered. Larger offsets are observed for GLONASS, up to 1 m for GLONASS K satellites. For Galileo the alignment of the broadcast orbit to IGS14/CODE is again at the 0.1 m and several milliarcsec level, with the FOC (Full Operational Capability) satellites slightly better than IOV (In Orbit Validation). For BeiDou an alignment of the broadcast frame to IGS14/CODE comparable to GLONASS is observed, regardless of whether IGSO (Inclined Geosynchronous Orbit) or MEO (Medium Earth Orbit) satellites are considered. For all satellites, position differences according to the broadcast ephemeris relative to IGS14/CODE orbits are projected to the radial, along-track and crosstrack triad, with the largest periodic differences affecting mostly the along track component. Sudden discontinuities at the level of up to 1 m and 2–3 ns are observed for the along-track component and the satellite clock, respectively. The time scales of GLONASS, Galileo, QZSS, SBAS and NAVIC are very closely aligned to GPS, with constant offsets depending on receiver type. The offset of the BeiDou time scale to GPS has an oscillatory pattern with peak-to-peak values up to 100 ns. To characterize receiver-dependent biases the average of six Septentrio receivers is taken as reference, and relative offsets of the other receiver types are investigated. These receiver-dependent biases may depend on the individual station, or for the same station on the update of the firmware. A detailed calibration history is presented for each multiGNSS station studied
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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