Two-scale Dirichlet-Neumann preconditioners for elastic problems with boundary refinements

The present work deals with the efficient resolution of elastostatics problems on domains with boundary refinements. The proposed approach separates the boundary refinements from the interior of the domain by the mortar method, and uses Dirichlet-Neumann preconditioners to solve the corresponding algebraic system. We prove that the simplest Dirichlet-Neumann algorithm achieves independence of the condition number of the preconditioned system with respect to the number and the size of the small details. Nevertheless, the situation no longer prevails when the refined boundary is clamped. An enhanced preconditioner is then designed by the introduction of a coarse space to mitigate the aforementioned sensitivity. Some numerical tests are performed to confirm the analysis, and the tools are extended by the proposition of a quasi-Newton method in the case of nonlinear elasticity. This paper is an extended version of a work presented at the DD16 conference with proofs and complete numerical results.     

Cultural and educational variations in maternal responsiveness.

Two separate studies examined the following hypotheses: (1) that maternal responsiveness is affected by cross-cultural differences in conventions of conversational interaction and (2) that maternal responsiveness is affected by intracultural differences in mothers' levels of formal education. The 1st study compared mother–infant interactions among the Gusii of Kenya with those in suburban Boston, Massachusetts. The 2nd study, carried out in the Mexican city of Cuernavaca, examined variations in mother–infant interactions by maternal schooling within a local sample of low-income mothers of similar cultural backgrounds who had attended school from 1 to 9 yrs. The 2 studies together indicate that maternal responsiveness during infancy, particularly in the verbal mode, is influenced by the mother's cultural background and school attendance (i.e., by factors that reflect her history of participation in institutionalized systems of communication and education). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis and crystal structure of Cu2NiO(B2O5) and Cu2MgO(B2O5)

A transport reaction synthesis technique has been used to prepare single crystals of two pyroborate compounds having the formulas Cu₂NiO(B₂O₅) and Cu₂MgO(B₂O₅). The two compounds are isostructural and crystallize in the monoclinic space group P2₁/c. Cu₂NiO(B₂O₅): a=3.2003(10), b=14.775(3), c=9.097(3), β=93.28(4), V=429.4(2) Å³, Z=4; and Cu₂MgO(B₂O₅): a=3.2401(6), b=14.790(2), c=9.147(2), β=94.88(2), V=436.7(2) Å³, Z=4. The structures of Cu₂NiO(B₂O₅) and Cu₂MgO(B₂O₅) were, respectively, refined from 804 and 1000 independent reflections to the final residuals R1=0.0366, wR2=0.0911 and R1=0.0231, wR2=0.0644. Both compounds exhibit a chevron-like structure built up of ribbons, made of edge-connected copper and nickel-oxygen polyhedra, running along the (1 0 0) direction. These ribbons are connected from one another via oxygen atoms and the cohesion of the three-dimensional network is ensured by [B₂O₅] entities. Cu in part occupies the position for Ni or Mg, so that the compounds actually are solid solution compounds. Ni or Mg atoms are octahedrally coordinated by oxygen, while the two pure Cu sites show [4] and [4+1] coordination, for Cu(1) and Cu(2), respectively. The ELNES B-K edge spectra for the two compounds support that the borate group present is [B₂O₅].     

In situ confocal-Raman measurement of water and methanol concentration profiles in Nafion membrane under cross-transport conditions

The local concentration gradients of water and methanol within a Nafion^® membrane are measured with a new microfluidic cell specially designed for depth measurement by confocal micro-Raman spectroscopy. The experimental concentration profiles of solvents, obtained in situ under cross-transport conditions, are fitted taking into account the contribution of the experimental set-up to the Raman response. This method allows to measure the concentration ratios of methanol and water at the solution–membrane interface as well as the real concentration gradients of these solvents within the membrane medium. These parameters are critical for a better understanding of membrane transport properties and cannot be directly measured by other techniques. Indeed, results here reported show that internal gradients differ from those that can be estimated from methods measuring external concentrations.     

Approximate regenerative-block bootstrap for Markov chains

The (approximate) regenerative block-bootstrap for bootstrapping general Harris Markov chains has recently been developed. It is built on the renewal properties of the chain, or of a Nummelin extension of the latter. It has theoretical properties that surpass other existing methods within the Markovian framework. The practical issues related to the implementation of this specific resampling method are discussed. Various simulation studies for investigating its performance and comparing it to other bootstrap resampling schemes, standing as natural candidates in the Markov setting are presented.     

Are the Logical Foundations of Verifying Compiler Prototypes Matching user Expectations?

The verifying compiler (VC) project proposals suggest that mainstream software developers are its targeted end-users. Like other software engineering efforts, the VC project success depends on appropriate end-user consultation. Industrial use of program assertions for the purpose of run-time assertion checking (RAC) is becoming commonplace. A likely next step on the path to VC adoption is the use of assertions in extended static checking (ESC), a fully automated form of static program verification (SPV). Unfortunately, all current VC prototypes supporting SPV, adopt a semantics which is unsound relative to the standard run-time interpretation of assertions. In this article, we report on the results of a survey in which we asked industrial developers what logical semantics they want program assertions to have, and whether consistency across RAC and SPV tools is important. Survey results indicate that developers are in favor of a semantics for assertions that is compatible with their current use in RAC.     

Distinguishing between natural and anthropogenic sources for elements in the environment: regional geochemical surveys versus enrichment factors

High element enrichment factors (EFs) are commonly used in the literature to support the hypothesis that a particular suite of elements is of anthropogenic origin. Real-world examples of regional geochemical surveys demonstrate that EFs can be high or low due to a multitude of reasons, of which contamination is but one. This applies to EFs calculated relative to either the crust or some local background (e.g., a deeper soil layer). Results from local studies near industrial centres showing high (and pollution-related) EFs cannot be generalised over large areas or for sample sites far removed (i.e., more than some tens of kilometers) from a likely pollution source. Regional-scale geochemical mapping, on the other hand, facilitates the reliable estimation of the influence of contamination on the measured element concentrations. EFs are strongly influenced by, among other factors, biogeochemical processes that redistribute chemical elements between environmental compartments at the Earth's surface. Using EFs to detect or 'prove' human influence on element cycles in remote areas should be avoided because, in most cases, high EFs cannot conclusively demonstrate, nor even suggest, such influence.