Il problema inverso del trasporto delle coordinate per geodetiche brevi e medie

Riassunto L'Autore elabora formule che servono per rappresentare l'intorno diWeingarten sulla sfera osculatrice, con ciò il problema inverso del trasporto delle coordinate sull'ellissoide viene ricondotto alla risoluzione di un triangolo sferico. Dimostra altresì che le formule della proiezione si potrebbero ottenere, almeno fino al secondo ordine, mediante la teoria dei minimi quadrati.

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Summary The Author elaborates the formulas giving the rapresentation ofWeingarten area on the osculatrix sphere; by means of these formulas the inverse problem of coordinate transport on the ellipsoid is reduced to the solution of a spheric triangle. The Author moreover proves that one can refine, at least to the second order, the same formulas making use of the least squares' theory.

     

Sulla variazione della densità nell'interno della terra

Riassunto L'Autore considera dapprima un geoide di rotazione di cui esprime la densità mediante sviluppo in serie di potenze del raggio vettore con i coefficienti dipendenti dalla latitudine . Risolve l'equazione di Poisson relativa al geoide, dimostra che la funzione potenziale si sviluppa in serie di potenze pari di e mette in evidenza la influenza dei termini dipendenti dalla latitudine nel rapporto fra i momenti di inerzia e nella variazione della gravità in superficie. Considera poi il geoide sferico e determina, in due esempi, l'andamento della densità, basandosi nel presupposto che l'energia del campo di gravità sia la più alta possibile compatibilmente allo stato attuale della Terra; ne risulta una densità centrale compresa fra 15 e 19.

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Summary The Author first considers a rotational geoid the density of which he introduces through potential series development of radius vector with coefficients as functions of latitude . He solves Poisson equation of the geoid, demonstrates that its potential function develops through potential series even of , points out the influence of the terms deriving from the latitude in the ratio from the inertia moments and the variation in surface gravity. Then he considers a spheric geoid and, by two demonstrations, he establishes the density, basing his theory on the assumption that gravity field energy is the highest one can trace in the present condition of the Earth; the result give a central density ranging from 15 to 19.

     

QMorphoStream: processing tools in QGIS environment for the quantitative geomorphic analysis of watersheds and river networks

The quantitative geomorphic analysis is a powerful tool for the study of geomorphology and landforms, as it provides objective methods to describe the main properties of drainage basins by means of an appropriate set of parameters. Over the last decades, GIS techniques and processing tools have been widely applied to the geomorphic analysis, and specific applications were developed, essentially using commercial software. In the present paper, the first experimental version of QMorphoStream, an originally developed set of processing tools for quantitative geomorphic analysis in QGIS environment, is presented. Besides the obvious advantage in terms of cost reduction, the choice of an open source development environment allowed us to integrate original algorithms with both QGIS built-in functions and processing tools available in the developers’ community.     

Stratigraphic constraints for explosive activity in the past 100 ka at Etna Volcano, Italy

The pyroclastic deposits of Etna have been correlated over the whole volcanic edifice for the first time, allowing the construction of a continuous record of tephra-producing events, which extends from approximately 100 ka to the Present. In this interval, five main periods of explosive activity have been identified: (a) ~100-ka strombolian to subplinian activity; (b) 80- to 100-ka plinian benmoreitic activity; (c) 16- to 80-ka strombolian to subplinian from basaltic to mugearitic activity; (d) 15.5- to 15-ka plinian benmoreitic activity accompanying the caldera-forming eruptions of the Ellittico Volcano; and (e) the most recent 13-ka basaltic explosive activity of strombolian and subplinian type of the present edifice that also includes the 122-B.C. plinian eruption. This study results in a semi-quantitative and in some cases quantitative definition of the intensity and chronology of the explosive activity at Etna. Moreover, this work gives a new significance to the volcanic hazards of Etna, a volcano generally considered to be the site of gentle effusive eruptions.     

Microalgal Communities of the Sea Ice, Ice-Covered and Ice-Free Waters of Wood Bay (Ross Sea, Antarctica) During the Austral Summer 1993 – 94

Abstract. During the austral summer 1993 – 94, microalgal density and biomass were investigated in the sea ice, in the underlying water column, in the melt water and during the formation of the sea ice. Of the 96 taxa identified, 59 were diatoms and 32 were dinoflagellates. Among the remaining five species, Pseudopleurochloris antarctica  was very abundant both in the sea ice and in the ice-free waters. Cell densities and biomass of microalgae were higher in the bottom of the sea ice and during the formation of the ice than in the seawater, and diatoms were the dominant group at higher microalgal biomass. Among these, Entomoneis kufferathii , Chaetoceros dichaeta and Fragilariopsis species were the most common taxa.     

Shake table testing on restoring capability of double concave friction pendulum seismic isolation systems

After an earthquake, non‐negligible residual displacements may affect the serviceability of a base isolated structure, if the isolation system does not possess a good restoring capability. The permanent offset does not affect the performance unless the design is problematic for utilities, also considering possible concerns related to the maintenance of the devices. Starting from experimental and analytical results of previous studies, the restoring capability of Double Concave Friction Pendulum bearings is investigated in this paper. A simplified design suggestion for the estimation of maximum expected residual displacements for currently used friction pendulum systems is then validated. The study is based on controlled‐displacement and seismic input experiments, both performed under unidirectional motion. Several shaking table tests have been carried out on a three‐dimensional isolated specimen structure. The same sequence of seismic inputs was applied considering three different conditions of sliding surfaces corresponding to low, medium and high friction. The accumulation of residual displacements is also investigated by means of nonlinear dynamic analysis. Copyright © 2017 John Wiley & Sons, Ltd.     

Experimental characterization,modeling and identification of the NEES‐UCSD shake table mechanical system

This paper proposes a simple conceptual mathematical model for the mechanical components of the NEES‐UCSD large high‐performance outdoor shaking table and focuses on the identification of the parameters of the model by using an extensive set of experimental data. An identification approach based on the measured hysteresis response is used to determine the fundamental model parameters including the effective horizontal mass, effective horizontal stiffness of the table, and the coefficients of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The effectiveness of the proposed conceptual model is verified through a comparison of analytical predictions with experimental results for various tests conducted on the system. The resulting mathematical model will be used in future studies to model the mechanical components of the shake table in a comprehensive physics‐based model of the entire mechanical, hydraulic, and electronic system. Copyright © 2007 John Wiley & Sons, Ltd.