Parallel solution to ill‐conditioned FE geomechanical problems

Parallel computers are potentially very attractive for the implementation of large size geomechanical models. One of the main difficulties of parallelization, however, relies on the efficient solution of the frequently ill‐conditioned algebraic system arising from the linearization of the discretized equilibrium equations. While very efficient preconditioners have been developed for sequential computers, not much work has been devoted to parallel solution algorithms in geomechanics. The present study investigates the state‐of‐the‐art performance of the factorized sparse approximate inverse (FSAI) as a preconditioner for the iterative solution of ill‐conditioned geomechanical problems. Pre‐and post‐filtration strategies are experimented with to increase the FSAI efficiency. Numerical results show that FSAI exhibits a promising potential for parallel geomechanical models mainly because of its almost ideal scalability. With the present formulation, however, at least 4 or 8 processors are required in the selected test cases to outperform one of the most efficient sequential algorithms available for FE geomechanics, i.e. the multilevel incomplete factorization (MIF). Further research is needed to improve the FSAI efficiency with a more effective selection of the preconditioner non‐zero pattern. Copyright © 2011 John Wiley & Sons, Ltd.     

Le barovariographe comme appareil de sondage aérologique

Summary First, the theory of the barovariograph, the deductions from which have also been confirmed by experiments, is presented with some improvements. Then there follows a concise illustration of the various possibilities of applying the instrument for the disclosure of aerological phenomena existing over a given locality.

---

Zusammenfassung Zunächst wird, mit einigen Erweiterungen, die Theorie des Barovariographen dargelegt, deren Ableitungen auch experimentell bestätigt wurden. Dann folgt eine kurze Erläuterung der verschiedenen Anwendungsmöglichkeiten des Instrumentes für die Registrierung gewisser aerologischer Erscheinungen über einem Ort.

---

Riasunto Dapprima viene esposta con alcuni perfezionamenti la teoria del barovariografo, le cui deduzioni sono state confermate anche sperimentalmente. Segue una illustrazione succinta delle varie possibilità applicative dello strumento per la rilevazione dei fenomeni aerologici sovrastanti una località determinata.

---

---

Communication présentée à l'Association Internationale de Météorologie, IXe Assemblée Générale de l'UGGI, Bruxelles, Séance du 24 Août 1951.     

Turbulent behaviour within a coastal boundary layer,observations and modelling at the Isola del Giglio

The hydrodynamics of coastal areas is characterized by the interaction among phenomena occurring at different spatial and temporal scales, such as the interaction of a large-scale ocean current with the local bathymetry and coastline, and local forcing conditions. In order to take into account all relevant phenomena, the study of the hydrodynamics of coastal zones requires a high-spatial and temporal resolution for both observations and simulation of local currents. This resolution can be obtained by using X-band radar, which allows simultaneous measurement of waves and currents in a range of 1–3 miles from the coastline, as well as high-resolution numerical models implemented in the area and configured through multiple nesting techniques in order to reach resolutions comparable to such coastal observations. Such an integrated monitoring system was implemented at the Isola del Giglio in 2012, after the accident of the Costa Concordia ship. Results can be used as a cross-validation of data produced independently by radar observations and numerical models. In addition, results give some important insights on the dynamics of the coastal boundary layer, both for what concerns the attenuation in the profile of the depth-averaged velocities which typically occur in turbulent boundary layers, as well as for the production, detachment and evolution of vorticity produced by the interaction of large-scale ocean currents with the coastline and the subsequent time evolution of such boundary layer. This transition between large-scale regional currents and the coastal boundary layer is often neglected in regional forecasting systems, but it has an important role in the ocean turbulence processes.     

Effects of inflationary bubbles on the polarization and temperature anisotropies of the cosmic microwave background

The broad X-ray iron line, detected in many active galactic nuclei, is likely to be produced by fluorescence from the X-ray-illuminated central parts of an accretion disc close to a supermassive black hole. The time-averaged shape of the line can be explained most naturally by a combination of special and general relativistic effects. Such line profiles contain information about the black hole spin and the accretion disc, as well as the geometry of the emitting region, and may help to test general relativity in the strong gravity regime. In this paper we embark on the computation of the temporal response of the line to the illuminating flux. Previous studies concentrated on the calculation of reverberation signatures from static sources illuminating the disc. In this paper we focus on the more physically justified case of flares located above the accretion disc and corotating with it. We compute the time-dependent iron line, taking into account all general relativistic effects, and show that its shape is of a very complex nature, and we also present light curves accompanying the iron line variability. We suggest that present and future X-ray satellites like XMM or Constellation-X may be capable of detecting features present in the computed reverberation maps.     

Strumento fotoelettrico per il calcolo del coefficiente di correlazione e per altri computi

Riassunto Si illustra un apparecchio fotoelettrico che, essendo atto al calcolo degli integrali doppi e degli integrali di numerose funzioni di funzione, si presta per determinare il coefficiente di correlazione.

---

Summary A photoelectric device is illustrated which, being fit for computation of double integrals, and for squaring a great number of functions of function, is suitable to determine the correlation coefficient.

     

SEM–EDS analysis of western Mediterranean obsidians: a new tool for Neolithic provenance studies

The contents of Na, Al, Si, K, Ca and Fe of 99 obsidians from the western Mediterranean islands of Lipari, Palmarola, Pantelleria and Sardinia were determined with the energy-dispersive spectrometer of a scanning electron microscope (SEM–EDS). The Na and in a lesser way other elements contents characterize any obsidian source-island. In Sardinia (80 samples), the four Monte Arci obsidian geochemical types can be discriminated from binary diagrams of element contents or by a discriminant analysis based on the six elements measured. It is concluded that SEM–EDS offers a new option for Neolithic obsidian provenance studies in this region. To cite this article: F.-X. Le Bourdonnec et al., C. R. Geoscience 338 (2006).     

Aquatic macrophyte diversity assessment: Validation of a new sampling method for circular-shaped lakes

We propose and validate a new sampling method to assess the presence, abundance and distribution of macrophytes in circular-shaped lakes according to the requirements of the Water Framework Directive (WFD2000/60/EC). The results of the macrophyte survey, and in particular of macrophyte diversity, obtained using this method are also discussed.The sampling is based on randomly selected transects homogeneously distributed around the perimeter of the lake. The number of transects is proportional to the lake's size. The method was validated on six Italian volcanic lakes using computational resampling procedures on a total of 126 transects.Using resampling procedures, we show that the proposed approach identifies more than 75% of the overall species richness through a moderate sampling effort. According to our results, Charophytes dominate aquatic vegetation in Italian volcanic lakes. Species diversity is highest at shallow depths, whereas the most abundant species, such as Chara polyacantha, are located at an intermediate depth between the shoreline and the maximum growing depth.