Liquefaction Potential and Vs30 Structure in the Middle-Chelif Basin, Northwestern Algeria, by Ambient Vibration Data Inversion

The Middle-Chelif basin, in northwestern Algeria, is located in a seismically active region. In its western part lies the El-Asnam fault, a thrust fault responsible for several strong earthquakes. The most important being the El-Asnam earthquake (Ms = 7.3) of 1980. In the present study, ambient vibration data with single-station and array techniques were used to investigate the dynamic properties of the ground and to estimate the Vs30 structure in the main cities of the basin. Soil resonance frequencies vary from 1.2 to 8.3 Hz with a maximum amplitude of 8.7 in. Collapsing behavior has also been demonstrated west of the city of El-Attaf, reflecting a strong potential for liquefaction. A Vs30 variation map and a soil classification for each city were obtained mainly by inversion of the HVSR and Rayleigh wave dispersion curves. Finally, an empirical prediction law of Vs30 for the Middle-Chelif basin was proposed

A Shear-Wave Velocity Model in the City of Oued-Fodda (Northern Algeria) from Rayleigh Wave Ellipticity Inversion

The city of Oued-Fodda is located in north-central Algeria on the margins of the Middle-Cheliff Basin. This region has suffered several destructive earthquakes. The strongest was the 1980 El-Asnam earthquake (Ms7.3), whose causative fault was located about 1 km north of the city of Oued-Fodda. Therefore, a good knowledge of the soil characteristics in this city may allow a better evaluation of the seismic risk and help to minimize damages in the future. With this objective, a detailed microzonation study of Oued-Fodda has been carried out in this study. For that, the horizontal-to-vertical spectral ratio (HVSR) method has been applied on 102 sites along the city, estimating the soil fundamental frequencies and their corresponding amplitudes. Besides, the Rayleigh wave ellipticity inversion has been accomplished in order to estimate the corresponding Vs profiles and provide two cross-sections of the geology under the city. In the central part of the city, high-frequency peaks are observed, between 12.5 and 15 Hz, which correspond to impedance contrasts at shallow depth (<20 m). In the surrounding plain, two clear peaks are identified in the ranges 1.8–3.5 Hz (fundamental frequencies) and 6.5–15 Hz (secondary peaks)

Shallow S-Wave Velocity Structure in the Middle-Chelif Basin, Algeria, Using Ambient Vibration Single-Station and Array Measurements

In order to better assess the seismic hazard in the northern region of Algeria, the shear-wave velocity structure in the Middle-Chelif Basin is estimated using ambient vibration single-station and array measurements. The Middle-Chelif Basin is located in the central part of the Chelif Basin, the largest of the Neogene sedimentary basins in northern Algeria. This basin hosts the El-Asnam fault, one of the most important active faults in the Mediterranean area. In this seismically active region, most towns and villages are built on large unconsolidated sedimentary covers. Application of the horizontal-to-vertical spectral ratio (HVSR) technique at 164 sites, and frequency–wavenumber (F–K) analysis at 7 other sites, allowed for the estimation of the ground resonance frequencies, shear-wave velocity profiles, and sedimentary cover thicknesses. The electrical resistivity tomography method was used at some sites to further constrain the thickness of the superficial sedimentary layers. The soil resonance frequencies range from 0.75 Hz to 12 Hz and the maximum frequency peak amplitude is 6.2. The structure of the estimated shear-wave velocities is presented in some places as 2D profiles to help interpret the existing faults. The ambient vibration data allowed us to estimate the maximum depth in the Middle-Chelif Basin, which is 760 m near the city of El-Abadia.This study was funded by the Consellería de Participación, Transparencia, Cooperación y Calidad Democrática de la Generalitat Valenciana, and by Research Group VIGROB-116 (University of Alicante)

Decision support tools for the design and dynamic reconfiguration of reconfigurable manufacturing systems

Les travaux de recherche effectués dans cette thèse traitent de l’optimisation dans la conception de lignes de production reconfigurables multi-produits. Ce type de lignes est caractérisé par leur capacité à traiter différents produits, où chacun d’entre eux nécessite une configuration adéquate de la ligne. Le passage d’une configuration de produit vers une autre implique que la ligne doit être reconfigurée en réaffectant certains tâches/modules entre les stations/machines disponibles. Ainsi, étant donné un ensemble de produits, les deux problèmes d’optimisation suivants sont étudiés. Le premier consiste à concevoir une configuration de ligne admissible pour chaque produit de telle sorte que le nombre de réaffectations de tâches soit minimisé. Le deuxième problème, quant à lui, vise à identifier le nombre minimal de modules nécessaire pour fabriquer tous les produits. Pour ces deux problèmes, nous avons initialement proposé une formulation PLNE. Ensuite, nous avons développé une approche heuristique, nommée Halt-and-Fix, pour le premier problème, et une méthode de décomposition pour le second. Ces deux problèmes ouvrent la voie à des perspectives de recherche intéressantes.The research work conducted in this thesis deals with the optimization in the design of multi-product reconfigurable lines. Such lines are characterized by their ability to handle different products, where each of them requires an appropriate line configuration. Moving from one product configuration to another means that the line has to be reconfigured by reassigning some tasks/modules be-tween the available stations/machines. Thus, given a set of products, the following two optimization problems are studied. The first one consists in designing an admissible line configuration for each product so that the number of task reassignments is minimized when switching between configurations. The second problem aims at identifying the minimum number of modules needed to manufacture all the products. For these two problems, we have proposed, at first, a MILP formulation. Subsequently, we have developed a heuristic approach, called Halt-and-Fix, for the first problem, and a decomposition method for the second. These two problems open the way to interesting research perspectives

Outils d'aide à la décision pour la mise en place et la configuration dynamique des lignes de production reconfigurables

The research work conducted in this thesis deals with the optimization in the design of multi-product reconfigurable lines. Such lines are characterized by their ability to handle different products, where each of them requires an appropriate line configuration. Moving from one product configuration to another means that the line has to be reconfigured by reassigning some tasks/modules be-tween the available stations/machines. Thus, given a set of products, the following two optimization problems are studied. The first one consists in designing an admissible line configuration for each product so that the number of task reassignments is minimized when switching between configurations. The second problem aims at identifying the minimum number of modules needed to manufacture all the products. For these two problems, we have proposed, at first, a MILP formulation. Subsequently, we have developed a heuristic approach, called Halt-and-Fix, for the first problem, and a decomposition method for the second. These two problems open the way to interesting research perspectives.Les travaux de recherche effectués dans cette thèse traitent de l’optimisation dans la conception de lignes de production reconfigurables multi-produits. Ce type de lignes est caractérisé par leur capacité à traiter différents produits, où chacun d’entre eux nécessite une configuration adéquate de la ligne. Le passage d’une configuration de produit vers une autre implique que la ligne doit être reconfigurée en réaffectant certains tâches/modules entre les stations/machines disponibles. Ainsi, étant donné un ensemble de produits, les deux problèmes d’optimisation suivants sont étudiés. Le premier consiste à concevoir une configuration de ligne admissible pour chaque produit de telle sorte que le nombre de réaffectations de tâches soit minimisé. Le deuxième problème, quant à lui, vise à identifier le nombre minimal de modules nécessaire pour fabriquer tous les produits. Pour ces deux problèmes, nous avons initialement proposé une formulation PLNE. Ensuite, nous avons développé une approche heuristique, nommée Halt-and-Fix, pour le premier problème, et une méthode de décomposition pour le second. Ces deux problèmes ouvrent la voie à des perspectives de recherche intéressantes

Minimizing task reassignments under balancing multi-product reconfigurable manufacturing lines

International audienceThis paper deals with optimization aspects of designing reconfigurable production lines with fixed number of workstations. The studied lines are characterized by their ability to handle multiple products, where switching from one product configuration to another is performed by reassigning certain tasks between workstations. Thus, given a set of products and the order of their arrival, the considered optimization problem consists in designing an admissible line configuration for each product such as the total number of task reassignments is minimized. An admissible line configuration can be viewed as a distribution of a given set of tasks among workstations subject to the corresponding cycle time and precedence constraints. To solve this problem, a mixed-integer linear program (MILP) is proposed. Then, an appropriate MILP-based heuristic, named as Halt-and-Fix, is developed to efficiently tackle large scale instances. Computational results are reported on a collection of instances derived from the well-known benchmark data used in the literature for the simple assembly line balancing problem. These results show that the heuristic has demonstrated a good overall performance when dealing with large size instances

An extended MILP formulation for the design of modular multi-model reconfigurable manufacturing lines

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A MILP-based heuristic approach for the design of multi-product modular reconfigurable lines

International audienc

A literature review of optimization problems for reconfigurable manufacturing systems

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