Dynamic reduction strategies to extend modal analysis approach at higher frequencies

Modal analysis on huge finite element models requires a numerical simplification in terms of total number of degrees of freedom (d.o.f.'s). The above aim is generally achieved by choosing some master d.o.f.'s and condensing the structure matrices on those d.o.f.'s. Static condensation (i.e. stiffness matrix reduction) is theoretically an errorless operation; on the other hand, mass condensation can only be approximate in dynamic applications. In order to accomplish matrix condensation, the technique mainly used is the so-called Guyan reduction. The present paper outlines the limitations of the technique, introducing some significant improvements. These are related to the inertia conservation properties of the reduced mass matrix and the condensed mass matrix assembly by means of fictitious and appropriate stiffness connections that are different from those obtained by the stiffness model. The effectiveness of the modified approach is demonstrated with respect to the modal analysis results obtained by Guyan approach, through three different test cases. (c) 2007 Elsevier B.V. All rights reserved

Intraplate transtensional tectonics in the East Antarctic Craton: insight from buried subglacial bedrock in the Lake Vostok – Dome C region

""This study presents the results of forward numerical models of a series of sections of the Aurora Trench (East Antarctica). derived from radio echo-sounding data that allowed to reconstruct the 3D shape of the Aurora Fault, a crustal listric. normal fault characterized by a length exceeding 100 km. A similar extensional fault setting allows to replicate the. asymmetric buried morphology of the magnetic basement at the Lake Vostok depression derived by the available gravity. and magnetic profiles. Both the Aurora and Vostok listric fault reach their basal decollment at 34 km depth, possibly. the base of the crust in this intracratonic environment. Integration of these results with the existing geologic interpretations. of the tectonic origin of the Concordia Trench by normal faulting allowed to frame the Concordia, Aurora and. Vostok normal faults within an intraplate transtensional corridor with a left-lateral movement component. The westward. projection of the proposed strike-slip deformation belt may develop in correspondence of an older tectonic lineament. stretching from the Eastern flanks of the Gamburtsev Subglacial Mts to the Lambert rift and characterized by a. poly-phased complex tectonic history. The possible Cenozoic reactivation of these structures is discussed in the paper."

Influence of coil contact on static behavior of helical compression springs

Large deformations of helical springs are affected by coil contact, but most available spring modelling techniques only account for nonlinear vertical motion, and Finite Elements (FE) nonlinear analysis that considers contact between coils can be very expensive. A 2D model based on equivalent beam and penalty-based contact algorithm is developed for efficient yet realistic prediction of non-uniform spring deflection. The proposed model is tested versus FE, where the helical wire is modelled using beam elements. Two scenarios are taken into account: a cylindrical spring in compression/bending and a progressive conical spring under simple compression. It is shown that the proposed model matches FE at a very low computational cost

A geomatic approach for emergency mapping of shallow landslides

Nel presente contributo viene proposto un approccio geomatico per mappare e caratterizzare dal punto di vista geomorfologico i fenomeni franosi superficiali in situazioni di emergenza. Il metodo è stato applicato durante il rilevamento di una frana che il 27/10/2013 ha interessato la falesia costiera della località "Baia dei Porci", nel Comune di Monte di Procida, in provincia di Napoli. Durante il rilevamento, eseguito parzialmente da barca, sono state scattate 95 foto successivamente elaborate con il software Agisoft PhotoScanTM. Il prodotto ottenuto dall'elaborazione è stato un modello digitale 3D della frana (DEM), georeferenziato nel sistema UTM 33N-WGS84. Dall'elaborazione del DEM eseguita in ESRI ArcGisTM è stato possibile ottenere la carta topografica della frana in scala 1:500, la carta delle pendenze, l'area delle zone di distacco e di deposito ed il volume del materiale franato. Visti i risultati ottenuti si ritiene che l'approccio proposto sia idoneo per essere applicato in situazioni di emergenza provocate da frane superficiali, a supporto delle autorità di Protezione Civile

Active Surface Structure of SnO2 Catalysts for CO2 Reduction Revealed by Ab Initio Simulations

Tin oxide (SnO2) is an efficient catalyst for the CO2 reduction reaction (CO2RR) to formic acid; however, the understanding of the SnO2 surface structure under working electrocatalytic conditions and the nature of catalytically active sites is a current matter of debate. Here, we employ ab initio density functional theory calculations to investigate how the selectivity and reactivity of SnO2 surfaces toward the CO2RR change at varying surface stoichiometry (i.e., reduction degree). Our results show that SnO2(110) surfaces are not catalytically active for the CO2RR or hydrogen evolution reaction, but rather they reduce under an applied external bias, originating surface structures exposing few metal tin layers, which are responsible for formic acid selectivity

Oral Lactoferrin in HIV-1 Vertically Infected Children: An Observational Follow-up of Plasma Viral Load and Immune Parameters

Lactoferrin (LF) is a mammalian iron-binding glycoprotein with antiviral effects. This preliminary study evaluated 6 months' LF (3 g/day, orally) treatment in 22 human immunodeficiency virus type 1 (HIV-1) vertically infected children. Plasma viral load and CD4+ cell counts were assessed every 3 months; before, during and after LF administration. No significant changes were observed during the pre-treatment period. By 6 months, mean (± SD) plasma viral load (log10) declined from 4.54 (± 0.65) to 4.28 (± 0.60); median percentage CD4+ cell count increased from 21.5% to 24.5%. Two months after treatment discontinuation, mean plasma viral load did not differ significantly from baseline or month 6 levels, but the percentage CD4+ cell count remained significantly higher than the baseline value. LF plus antiretroviral (ARV) therapy was more effective at increasing CD4+ cell count than LF alone. None of the patients showed any new HIV-1-related symptoms at follow-up. LF might be a useful addition to ARV therapy, ..

SFM-MVS photogrammetry for rockfall analysis and hazard assessment along the ancient roman via Flaminia road at the Furlo gorge (Italy)

Rockfall events represent significant hazards for areas characterized by high and steep slopes and therefore effective mitigation controls are essential to control their effect. There are a lot of examples all over the world of anthropic areas at risk because of their proximity to a rock slope. A rockfall runout analysis is a typical 3D problem, but for many years, because of the lack of specific software, powerful computers, and economic reasons, a 2D approach was normally adopted. However, in recent years the use of 3D software has become quite widespread and different runout working approaches have been developed. The contribution and potential use of photogrammetry in this context is undoubtedly great. This paper describes the application of a 3D hybrid working approach, which considers the integrated use of traditional geological methods, Terrestrial Laser Scanning, and drone based Digital Photogrammetry. Such approach was undertaken in order to perform the study of rockfall runout and geological hazard in a natural slope in Italy in correspondence of an archaeological area. Results show the rockfall hazard in the study area and highlights the importance of using photogrammetry for the correct and complete geometrical reconstruction of slope, joints, and block geometries, which is essential for the analysis and design of proper remediation measures

A GPU-based survey for millisecond radio transients using ARTEMIS

Astrophysical radio transients are excellent probes of extreme physical processes originating from compact sources within our Galaxy and beyond. Radio frequency signals emitted from these objects provide a means to study the intervening medium through which they travel. Next generation radio telescopes are designed to explore the vast unexplored parameter space of high time resolution astronomy, but require High Performance Computing (HPC) solutions to process the enormous volumes of data that are produced by these telescopes. We have developed a combined software /hardware solution (code named ARTEMIS) for real-time searches for millisecond radio transients, which uses GPU technology to remove interstellar dispersion and detect millisecond radio bursts from astronomical sources in real-time. Here we present an introduction to ARTEMIS. We give a brief overview of the software pipeline, then focus specifically on the intricacies of performing incoherent de-dispersion. We present results from two brute-force algorithms. The first is a GPU based algorithm, designed to exploit the L1 cache of the NVIDIA Fermi GPU. Our second algorithm is CPU based and exploits the new AVX units in Intel Sandy Bridge CPUs.Comment: 4 pages, 7 figures. To appear in the proceedings of ADASS XXI, ed. P.Ballester and D.Egret, ASP Conf. Se