A hybrid optimization technique coupling an evolutionary and a local search algorithm

Evolutionary algorithms are robust and powerful global optimization techniques for solving large-scale problems that have many local optima. However, they require high CPU times, and they are very poor in terms of convergence performance. On the other hand, local search algorithms can converge in a few iterations but lack a global perspective. The combination of global and local search procedures should offer the advantages of both optimization methods while offsetting their disadvantages. This paper proposes a new hybrid optimization technique that merges a genetic algorithm with a local search strategy based on the interior point method. The efficiency of this hybrid approach is demonstrated by solving a constrained multi-objective mathematical test-case.     

Aggregation of laponite in the presence of magnesium ions and polyacrylic acid

The average mass and size characteristics of ageing laponite/MgCl₂ and laponite/MgCl₂/polyacrylic acid were determined in aqueous dispersions at pH 10 using a Coulter counter and laser diffractometry methods. Comparison between mass and size characteristics showed the two systems to temporarily acquire a structure where particles are more densely packed. The relatively higher packing observed for laponite/polymer was attributed to conformational changes of the polymer adsorbed on neighbouring surfaces. Analysis of the reduced mass and size distribution functions confirmed the self-similarity of the distributions. The reduced mass frequency continuously decreased, while the reduced size frequency showed a linear decrease combined with bell-shaped populations. The volume packing observed for the laponite/polymer was attributed to a typical class of aggregates of large size, which was present at the maximal concentration in the bell-shaped distribution. Received: 19 February 2001 Accepted: 6 April 2001     

Numerical zoom for advection diffusion problems with localized multiscales

We investigate the Schwarz'domain decomposition algorithm for numerical zooms. Error estimates are given for nonmatching meshes for elliptic and parabolic partial differential equations. The method is applied to the security assessment of the burial of nuclear waste which is a typical multiscale problem for porous media flow. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010     

The Ultra-Quasi-Metrically Injective Hull of a T 0-Ultra-Quasi-Metric Space

Jointly with E. Kemajou, in previous work we constructed the so-called Isbell-hull of a T ₀-quasi-metric space. In this article we continue these investigations by presenting a similar construction in the category of T ₀-ultra-quasi-metric spaces and contracting maps. Comparable studies in the area of ultra-metric spaces have been conducted before by Bayod and Martínez-Maurica.     

Another complete invariant for Steiner triple systems of order 15

In this note, the 80 non‐isomorphic triple systems on 15 points are revisited from the viewpoint of the convex hull of the characteristic vectors of their blocks. The main observation is that the numbers, of facets of these 80 polyhedra are all different, thus producing a new proof of the non‐isomorphism of these triple systems. The space dimension of these polyhedra is also discussed. Finally, we observe the large number of facets of some of these polyhedra with few vertices, in relation with the upper bound problem for combinatorial polyhedra. © 2005 Wiley Periodicals, Inc. J Combin Designs.     

An exact and polynomial distance-based algorithm to reconstruct single copy tandem duplication trees

The problem of reconstructing the duplication tree of a set of tandemly repeated sequences which are supposed to have arisen by unequal recombination, was first introduced by Fitch (1977), and has recently received a lot of attention. In this paper, we place ourselves in a distance framework and deal with the restricted problem of reconstructing single copy duplication trees. We describe an exact and polynomial distance based algorithm for solving this problem, the parsimony version of which has previously been shown to be NP-hard (like most evolutionary tree reconstruction problems). This algorithm is based on the minimum evolution principle, and thus involves selecting the shortest tree as being the correct duplication tree. After presenting the underlying mathematical concepts behind the minimum evolution principle, and some of its benefits (such as statistical consistency), we provide a new recurrence formula to estimate the tree length using ordinary least-squares, given a matrix of pairwise distances between the copies. We then show how this formula naturally forms the dynamic programming framework on which our algorithm is based, and provide an implementation in O(n³) time and O(n²) space, where n is the number of copies.     

Deglycosylation of glucose oxidase to improve biosensors and biofuel cells

We demonstrate that a more efficient redox hydrogel structure can be achieved by engineering the size and the surface charge of the bioelectrocatalyst. Deglycosylated glucose oxidase (GOx) modified electrode exhibits higher current density than native GOx, for the same molar composition of the hydrogel. This improvement is very likely due to a more efficient hydrogel structure rather than a better intrinsic electron transfer between the FAD/FADH₂ redox center and the redox mediator.     

Zur gravimetrischen Bestimmung des Phenols

Ohne Zusammenfassung