Search results for "convergence"
showing 10 items of 655 documents
The Role of Public Entity in Coopetiotion and Convergence
2007
We investigate upon the strategic impact of the public entity to catalyze coalition formation among competitors around an essential facility. The public entity is usually represented as if moved by mere political scopes. However, the presence of a publicly-owned asset or infrastructure, which can be termed an essential facility, gives leeway to shed the opportunity to satisfy potentially new and different type of demand or consumer cluster needs. The increase in value stemming from a renewal in the utilization of the facility might loosen up political restraints against the involvement in the management of the facility of a multiplicity of actors. This allows us to add a new dimension to th…
Parallelization of adaptive MC integrators
1997
Monte Carlo (MC) methods for numerical integration seem to be embarassingly parallel on first sight. When adaptive schemes are applied in order to enhance convergence however, the seemingly most natural way of replicating the whole job on each processor can potentially ruin the adaptive behaviour. Using the popular VEGAS-Algorithm as an example an economic method of semi-micro parallelization with variable grain-size is presented and contrasted with another straightforward approach of macro-parallelization. A portable implementation of this semi-micro parallelization is used in the xloops-project and is made publicly available.
Dual Inequalities for Stabilized Column Generation Revisited
2014
Column generation (CG) models have several advantages over compact formulations: they provide better linear program bounds, may eliminate symmetry, and can hide nonlinearities in their subproblems. However, users also encounter drawbacks in the form of slow convergence, also known as the tailing-off effect, and the oscillation of the dual variables. Among different alternatives for stabilizing the CG process, Ben Amor et al. [Ben Amor H, Desrosiers J, Valério de Carvalho JM (2006) Dual-optimal inequalities for stabilized column generation. Oper. Res. 54(3):454–463] suggest the use of dual-optimal inequalities (DOIs) in the context of cutting stock and bin packing problems. We generalize th…
A coupled cluster study of the 1 1A1g and 1 1B2u states of benzene
1998
A theoretical investigation of the equilibrium structures and harmonic frequencies of the 1 1A1g and 1 1B2u states of benzene is presented. The performance of coupled cluster singles (CCS), the recently proposed CC2 model, and coupled cluster singles and doubles (CCSD) is compared. The CC2 ground and excited states frequencies are a significant improvement of the CCS results and are relatively close to the CCSD results. A comparative analysis of the vibrations in the two electronic states of both C6H6 and C6D6 is presented. The reliability of predicted shifts in harmonic frequencies between the two states and isotopic shifts is estimated on the basis of the convergence in the CCS, CC2, and …
An adaptive method for Volterra–Fredholm integral equations on the half line
2009
AbstractIn this paper we develop a direct quadrature method for solving Volterra–Fredholm integral equations on an unbounded spatial domain. These problems, when related to some important physical and biological phenomena, are characterized by kernels that present variable peaks along space. The method we propose is adaptive in the sense that the number of spatial nodes of the quadrature formula varies with the position of the peaks. The convergence of the method is studied and its performances are illustrated by means of a few significative examples. The parallel algorithm which implements the method and its performances are described.
Convergence of inertial prox-penalization and inertial forward-backward algorithms for solving bilevel monotone equilibrium problems
2023
The main focus of this paper is on bilevel optimization on Hilbert spaces involving two monotone equilibrium bifunctions. We present a new achievement consisting on the introduction of inertial methods for solving this type of problems. Indeed, two several inertial type methods are suggested: a proximal algorithm and a forwardbackward one. Under suitable conditions and without any restrictive assumption on the trajectories, the weak and strong convergence of the sequence generated by the both iterative methods are established. Two particular cases illustrating the proposed methods are thereafter discussed with respect to hierarchical minimization problems and equilibrium problems under a sa…
Weak and strong convergence of an inertial proximal method for solving bilevel monotone equilibrium problems
2022
In this paper, we introduce an inertial proximal method for solving a bilevel problem involving two monotone equilibrium bifunctions in Hilbert spaces. Under suitable conditions and without any restrictive assumption on the trajectories, the weak and strong convergence of the sequence generated by the iterative method are established. Two particular cases illustrating the proposed method are thereafter discussed with respect to hierarchical minimization problems and equilibrium problems under saddle point constraint. Furthermore, a numerical example is given to demonstrate the implementability of our algorithm. The algorithm and its convergence results improve and develop previous results i…
Inter-Relationships Between Groundnut Yield in Senegal, Interannual Rainfall Variability and Sea-Surface Temperatures
1999
Groundnut production strongly contributes to Senegal’s economy. Interannual variations of groundnut yield for the country as a whole, and their relationship with rainfall amounts, are examined for the 31-yr period 1960–1990. It is shown that on that scale, and after removing decadal trends, almost half of the variance is explained by rainfall variability, especially that of the early part of the rainy season (July–August). Given the high spatial coherence of seasonal rainfall in the region, teleconnections with global- and regional-scale climate dynamics, including sea-surface temperatures, are assessed. Though some features are similar to the rest of the Sahel, others are more specific, su…
The East African March–May Rainy Season: Associated Atmospheric Dynamics and Predictability over the 1968–97 Period
2002
Abstract This paper focuses on the East African March–May “long rains.” Particularly, it investigates the atmospheric patterns associated to the March–May rainfall anomalies, then proposes a seasonal prediction model. In a preliminary step, in order to define a regional rainfall index, a new form of extended principal component analysis is performed, aimed at capturing both the spatial and intraseasonal rainfall coherence. What emerges is that although the long rains exhibit a low temporal coherence, calling for a separation between the months of March–April and May in teleconnection studies, they show a relatively strong spatial consistency over the Kenya–Uganda inland region. From composi…
Intraseasonal wind anomalies related to wet and dry spells during the ?long? and ?short? rainy seasons in Kenya
1997
The largest part of Kenya exhibits two major rainy seasons, the March–May «long rains» and the October–December «short rains», both related to the passage of the ITCZ, but differing in the amount of rainfall recorded and its interannual variability. In order to investigate whether these differences also apply at intraseasonal time-scales, daily rainfall data for the peak month of each rainy season (April and November) were collected for 7 consecutive years (1982–1988). The network comprises 68 stations, from which a classification of the spatial patterns of daily rainfall anomalies has been performed. Wind anomalies corresponding to the various rainfall types and to specific regional rainfa…