Multigrid for Qk finite element matrices using a (block) Toeplitz symbol approach

In the present paper, we consider multigrid strategies for the resolution of linear systems arising from the Qk Finite Elements approximation of one-and higher-dimensional elliptic partial differential equations with Dirichlet boundary conditions and where the operator is div (-a(x) 07\u2022), with a continuous and positive over \u3a9, \u3a9 being an open and bounded subset of R2. While the analysis is performed in one dimension, the numerics are carried out also in higher dimension d 65 2, showing an optimal behavior in terms of the dependency on the matrix size and a substantial robustness with respect to the dimensionality d and to the polynomial degree k

The Green, Green Grass of Home: an archaeo-ecological approach to pastoralist settlement in central Kenya

© 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This paper considers the ecological residues of pastoralist occupation at the site of Maili Sita in Laikipia, central Kenya, drawing links with the archaeological record so as to contribute a fresh approach to the ephemeral settlement sites of mobile herding communities, a methodological aspect of African archaeology that remains problematic. Variations in the geochemical and micromorphological composition of soils along transects across the site are compared with vegetation distributions and satellite imagery to propose an occupation pattern not dissimilar to contemporary Cushitic-speaking groups further north. We argue that Maili Sita exemplifies the broad migratory and cultural exchange networks in place during the mid- to late second millennium AD, with pastoralist occupants who were both physically and culturally mobile.British Academy (2002-5 Funding) European Union - Marie Curie Initiatives (EXT grant 2007-11

Optimal preconditioning for image deblurring with Anti-Reflective boundary conditions

Inspired by the theoretical results on optimal preconditioning stated by Ng, Chan, and Tang in the framework of Reflective boundary conditions (BCs), in this paper we present analogous results for Anti-Reflective BCs. Here a key technical difficulty is represented by the non-orthogonal character of the Anti-Reflective transform and indeed the proof proposed by Ng, Chan, and Tang does not work. Nevertheless, in both cases, the optimal preconditioner is the blurring matrix associated to the symmetrized Point Spread Function (PSF). The geometrical idea on which our proof is based is very simple and general, so it may be useful in the future to prove theoretical results for new proposed BCs. Numerical tests show that the optimal preconditioning strategy is effective when using both preconditioned conjugate gradient methods and recently introduced nonstationary preconditioned iterations

Are Household Production Decisions Cooperative? Evidence on Pastoral Migration and Milk Sales from Northern Kenya

Market-based development efforts frequently create opportunities to generate income from goods previously produced and consumed within the household. Production within the household is often characterized by a gender and age division of labor. Market development efforts to improve well-being may lead to unanticipated outcomes if household production decisions are noncooperative. We develop and test models of household decision making to investigate intrahousehold decision making in a nomadic pastoral setting from Kenya. Our results suggest that household decisions are contested, with husbands using migration decisions to resist wives' ability to market milk. Copyright 2006, Oxford University Press.

The Green, Green Grass of Home : an archaeo-ecological approach to pastoralist settlement in central Kenya

This paper considers the ecological residues of pastoralist occupation at the site of Maili Sita in Laikipia, central Kenya, drawing links with the archaeological record so as to contribute a fresh approach to the ephemeral settlement sites of mobile herding communities, a methodological aspect of African archaeology that remains problematic. Variations in the geochemical and micromorphological composition of soils along transects across the site are compared with vegetation distributions and satellite imagery to propose an occupation pattern not dissimilar to contemporary Cushitic-speaking groups further north. We argue that Maili Sita exemplifies the broad migratory and cultural exchange networks in place during the mid- to late second millennium AD, with pastoralist occupants who were both physically and culturally mobile