n/a

We establish a Fredholm criterion for an arbitrary operator in the Banach algebra of singular integral operators
with piecewise continuous coefficients on Nakano spaces (generalized Lebesgue spaces with variable exponent) with Khvedelidze weights over Carleson curves with logarithmic whirl points.

A classical theorem of Coifman, Rochberg, and Weiss on commutators of singular integrals is extended to the case of generalized Lp spaces with variable exponent.

Given a complete rewriting system R on X and a subset X0 of X+ satisfying certain conditions, we present a complete rewriting system for the submonoid of M(X;R) generated by X0. The obtained result will be applied to the group of units of a monoid satisfying H1 = D1. On the other hand we prove that all maximal subgroups of a monoid defined by a special rewriting system are isomorphic.

This thesis deals with the analysis of the behaviour of retrofitting reinforced concrete circular columns with FRP materials which were subjected either to axial cyclic compression or axial compression and alternated cyclic horizontal loads. The choice of this topic derived from the need to investigate the behaviour of the strengthening of reinforced concrete columns to seismic actions, especially with new materials such as carbon and glass fibres or polymeric mortars. Another reason for such choice is linked to the strong seismicity of the Portuguese territory.
It has been verified that confined concrete columns with FRP jackets have their resistance and ductility highly increased as these considerably reduce the columns transversal deformation, thus preventing the buckling of longitudinal reinforcement. There has been an increasing use of FRP composites in the strengthening of structures, mainly with GFRP (Glass Fibre Reinforced Plastics) or CFRP (Carbon Fibre Reinforced Plastics). This is due to their attractive characteristics such as high resistance to corrosion, lowratio for weight/strength, moldability, easy application and the fact that there is no need of support structures.
Forty-five experimental tests were carried out, dealing with retrofitting reinforced concrete columns with axial monotonic or cyclic compression reinforced with FRP composites. The column height of 750 mm was maintained in order to evaluate the influence of several parameters in its behaviour: the column geometry (change in its diameter), the type of column (plain or reinforced concrete), transversal reinforcement ratio of concrete columns, the type of external confinement with FRP (C or GFRP), the number of FRP layers and the type of axial loading (monotonic or cyclic).
Twelve additional experimental tests were conducted in order to analyse the behaviour of reinforced concrete columns jacketed with FRP composites and subjected to axial cyclic compression and alternated cyclic horizontal loads. The columns’ dimension was maintained (1500 mm height by 250 mm diameter) and the models were subjected to a series of cyclic and alternated loadings. This enabled the study of the various parameters’ influence in their behaviour such as the type of FRP confinement, the number of FRP layers, the level of axial loading, the jacket’s height or the strengthening of the plastic hinge by replacing the cover concrete with polymeric mortar.
Based on the numerical models presented and experimental analysis carried out, models were proposed and developed to simulate the behaviour of columns jacketed with FRP composites.

n/a

n/a

n/a

If H is a family of graphs, then an H-decomposition of a graph G is a partition of the edges of G each element of which induces a copy of a graph in G.
This paper addresses the problem of finding the number φ(n,H), the smallest number k such that every graph on n vertices has an H-decomposition with at most k elements. φ(n,H) is found in the cases when H={K2,C5}; when H={K2,C5+e}, where e is a chord of the C5; when H={K2,K4−e}; and when H={K2,K3+e}, where e is a pendant edge added to one vertex in the K3.

A multi-product model for the design of global supply chains with reverse flows is proposed. Two levels of decisions are considered, one strategic and one tactical. The first is modelled through a macro perspective of time where the determination of the network structure and flows is accomplished. At tactical level, a micro perspective of time is considered, where production planning and inventory management are addressed in detail. A mixed integer linear programming formulation is developed which is solved with standard Branch and Bound techniques. The model accuracy and suitability are studied using a case study.

{Summary: We are interested in an adequate estimation of the dominant component of the bias of ıt B. M. Hill}\,'s estimator [Ann. Stat. 3, 1163–1174 (1975; Zbl 0323.62033)] of a positive tail index $\gamma$, in order to remove it from the classical Hill estimator in different asymptotically equivalent ways. If the second order parameters in the bias are computed at an adequate level $k_1$ of a larger order than that of the level $k$ at which the Hill estimator is computed, there may be no change in the asymptotic variances of these reduced bias tail index estimators, which are kept equal to the asymptotic variance of the Hill estimator, i.e., equal to $\gamma^2$. The asymptotic distributional properties of the proposed estimators of $\gamma$ are derived and the estimators are compared not only asymptotically, but also for finite samples through Monte Carlo techniques.}