Objective multiscale analysis of random heterogeneous materials

The multiscale framework presented in [1, 2] is assessed in this contribution for a study of random heterogeneous materials. Results are compared to direct numerical simulations (DNS) and the sensitivity to user-defined parameters such as the domain decomposition type and initial coarse scale resolution is reported. The parallel performance of the implementation is studied for different domain decompositions

BDDC and FETI-DP under Minimalist Assumptions

The FETI-DP, BDDC and P-FETI-DP preconditioners are derived in a particulary simple abstract form. It is shown that their properties can be obtained from only on a very small set of algebraic assumptions. The presentation is purely algebraic and it does not use any particular definition of method components, such as substructures and coarse degrees of freedom. It is then shown that P-FETI-DP and BDDC are in fact the same. The FETI-DP and the BDDC preconditioned operators are of the same algebraic form, and the standard condition number bound carries over to arbitrary abstract operators of this form. The equality of eigenvalues of BDDC and FETI-DP also holds in the minimalist abstract setting. The abstract framework is explained on a standard substructuring example.Comment: 11 pages, 1 figure, also available at http://www-math.cudenver.edu/ccm/reports

Taxing the powerful, the rise of populism and the crisis in Europe: the case for the EU Common Consolidated Corporate Tax Base

Contemporary populism is rooted in a crisis of legitimacy. Corporate taxavoidance by multinationals is one cause of that crisi s. Although states tend to beincreasingly formally committed to tackling avoidance, they do so in a system thatpromotes contradictory sets of behaviour. This tends to undermine attempts to solvethe problem of avoidance unless a more transformative collective approach is taken.Ironically, despite its own democratic deficit, the European Comm ission has taken aleading role in promoting such a solution: the Common Consolidated Corporate TaxBase (CCCTB). In this paper, I set out the case for ‘unitary taxation’ based on theCCCTB and state some of its current problems. The problem of corporation taxraises a basic issue in terms of who is sovereignty for, and solving the problemprovides an important contribution to legitimacy of both the state and the EU

EDDY PROCESSES OF THE WESTERN ADRIATIC CURRENT NEAR CAPE GARGANO

Abstract Eddy processes of the Western Adriatic Current near Cape Gargano are highly modulated by the wind, growing during calm periods following strong wind events. Both single anticyclones and trains of multiple eddies with a regular spacing are observed. Suppression of a single anticyclone in the lee of the Cape was observed by profiling SEPTR moorings to occur when the horizontal gradient of the thermocline depth was increased by the wind. Eddies also form cyclonic filaments extending offshore. Such a filament was observed through the new technique of seismic oceanography to have downslope tilting isotherms and a long, thin, offshore extension in the bottom boundary layer. Recent measurements from two international collaborative research programs reveal new details of eddy activity and instability of the Western Adriatic Current (WAC) as it rounds Cape Gargano in the central Adriatic Sea. The "Dynamics of the Adriatic in Real-Time" (DART) program was focused on understanding the predictability of this system with observation and modelling from October 2005 through September 2006. These included, among other things, measurements from long-term current moorings, profiling SEPTR moorings, tow-yo CTD profiles, remote sensing, and high-resolution modelling using the U.S. Navy Coastal Ocean Model. Remote sensing and modelling, supported by in situ observations, revealed two distinct cases of WAC eddy activity Although Adriatic wind regimes and Cape topography provide the background setting for eddy formation, frontal instabilities and mixing processes determine many details of eddy structure and evolution. Acknowledgments: We thank the Italian CNR for providing R/V Urania ship time and CNR-ISMAR for coordinating the AdriaSeismic09 cruise

Vegetation type, not the legacy of warming, modifies the response of microbial functional genes and greenhouse gas fluxes to drought in oro-arctic and alpine regions

Climate warming and summer droughts alter soil microbial activity, affecting greenhouse gas (GHG) emissions in arctic and alpine regions. However, the long-term effects of warming, and implications for future microbial resilience, are poorly understood. Using one alpine and three arctic soils subjected to in situ long-term experimental warming, we simulated drought in laboratory incubations to test how microbial functional-gene abundance affects fluxes in three GHGs: carbon dioxide, methane, and nitrous oxide. We found that responses of functional gene abundances to drought and warming are strongly associated with vegetation type and soil carbon. Our sites ranged from a wet, forb dominated, soil carbon-rich systems to a drier, soil carbon-poor alpine site. Resilience of functional gene abundances, and in turn methane and carbon dioxide fluxes, was lower in the wetter, carbon-rich systems. However, we did not detect an effect of drought or warming on nitrous oxide fluxes. All gene-GHG relationships were modified by vegetation type, with stronger effects being observed in wetter, forb-rich soils. These results suggest that impacts of warming and drought on GHG emissions are linked to a complex set of microbial gene abundances and may be habitat-specific

Characterizing, modelling and understanding the climate variability of the deep water formation in the North-Western Mediterranean Sea

Observing, modelling and understanding the climate-scale variability of the deep water formation (DWF) in the North-Western Mediterranean Sea remains today very challenging. In this study, we first characterize the interannual variability of this phenomenon by a thorough reanalysis of observations in order to establish reference time series. These quantitative indicators include 31 observed years for the yearly maximum mixed layer depth over the period 1980–2013 and a detailed multi-indicator description of the period 2007–2013. Then a 1980–2013 hindcast simulation is performed with a fully-coupled regional climate system model including the high-resolution representation of the regional atmosphere, ocean, land-surface and rivers. The simulation reproduces quantitatively well the mean behaviour and the large interannual variability of the DWF phenomenon. The model shows convection deeper than 1000 m in 2/3 of the modelled winters, a mean DWF rate equal to 0.35 Sv with maximum values of 1.7 (resp. 1.6) Sv in 2013 (resp. 2005). Using the model results, the winter-integrated buoyancy loss over the Gulf of Lions is identified as the primary driving factor of the DWF interannual variability and explains, alone, around 50 % of its variance. It is itself explained by the occurrence of few stormy days during winter. At daily scale, the Atlantic ridge weather regime is identified as favourable to strong buoyancy losses and therefore DWF, whereas the positive phase of the North Atlantic oscillation is unfavourable. The driving role of the vertical stratification in autumn, a measure of the water column inhibition to mixing, has also been analyzed. Combining both driving factors allows to explain more than 70 % of the interannual variance of the phenomenon and in particular the occurrence of the five strongest convective years of the model (1981, 1999, 2005, 2009, 2013). The model simulates qualitatively well the trends in the deep waters (warming, saltening, increase in the dense water volume, increase in the bottom water density) despite an underestimation of the salinity and density trends. These deep trends come from a heat and salt accumulation during the 1980s and the 1990s in the surface and intermediate layers of the Gulf of Lions before being transferred stepwise towards the deep layers when very convective years occur in 1999 and later. The salinity increase in the near Atlantic Ocean surface layers seems to be the external forcing that finally leads to these deep trends. In the future, our results may allow to better understand the behaviour of the DWF phenomenon in Mediterranean Sea simulations in hindcast, forecast, reanalysis or future climate change scenario modes. The robustness of the obtained results must be however confirmed in multi-model studies