Multicriterion Scantling Optimization of the Midship Section of a Passenger Vessel considering IACS Requirements

peer reviewedIn the scantling design of a passenger ship, minimum production cost, minimum weight and maximum moment of inertia (stiffness) are conflicting objectives. For that purpose, recent improvements were made to the LBR-5 software (French acronym of “Stiffened Panels Software”, version 5.0) to optimize the scantling of ship sections by considering production cost, weight and moment of inertia in the optimization objective function. Moreover, IACS requirements regarding bending, shearing and buckling strength are currently available in LBR-5. Until now, only raw scantling optimizations were performed with LBR-5. Thanks to new developments using heuristics, it is now possible to realize discrete optimization so that a standardized and “ready to use” set of optimum scantlings can be obtained

Minimization of Production Cost by use of an Automatic Cost Assessment Method and Simulation

peer reviewedThis paper will present different ways to minimize cost in shipbuilding industry. Amongst them we have the production simulation methods, the cost assessment methods and the optimization methods. Nowadays, cost assessment is a key task of an integrated ship design. The various methods to estimate the production cost differ with the known information (input data). The less information is detailed, the earlier a method can be used in the design process. The more information is used, the better we can assess the differences between design alternatives. The methods presented here and the “design for production” concept promise to increase the productivity trough the following points: a more accurate cost estimation, an improvement in the deadlines planning and the production schedule, a progress in distribution of the workload between the various production workshops, a better knowledge of the individual costs that will permit to reduce the global cost. In order to illustrate our work, we present in this paper three methods to decrease the global cost of a ship

OptiView − A Powerful and Flexible Decision Tool Optimising Space Allocation in Shipyard Workshops

peer reviewedThis paper presents new developments to maximize the number of ship blocks and ship sections produced in various workshops of shipyards during a certain time window. The visualization tool OptiView® was developed to support users to improve the space utilization and workshop productivity. The software is coupled with a heuristic optimisation solver. The paper describes the approach to the space allocation problem and gives three application examples

Assessing and adjusting for differences between HIV prevalence estimates derived from national population-based surveys and antenatal care surveillance, with applications for Spectrum 2013

Objective(s): To assess differences between HIV prevalence estimates derived from national population surveys and antenatal care (ANC) surveillance sites and to improve the calibration of ANC-derived estimates in Spectrum 2013 to more appropriately account for differences between these data. Design: Retrospective analysis of national population survey and ANC surveillance data from 25 countries with generalized epidemics in sub-Saharan Africa and 8 countries with concentrated epidemics. Methods: Adult national population survey and ANC surveillance HIV prevalence estimates were compared for all available national population survey data points for the years 1999–2012. For sub-Saharan Africa, a mixed-effects linear regression model determined whether the relationship between national population and ANC estimates was constant across surveys. A new calibration method was developed to incorporate national population survey data directly into the likelihood for HIV prevalence in countries with generalized epidemics. Results were used to develop default rules for adjusting ANC data for countries with no national population surveys. Results: ANC surveillance data typically overestimate population prevalence, although a wide variation, particularly in rural areas, is observed across countries and survey years. The new calibration method yields similar point estimates to previous approaches, but leads to an average 44% increase in the width of 95% uncertainty intervals. Conclusion: Important biases remain in ANC surveillance data for HIV prevalence. The new approach to model-fitting in Spectrum 2013 more appropriately accounts for this bias when producing national estimates in countries with generalized epidemics. In countries with concentrated epidemics, local sex ratios should be used to calibrate ANC surveillance estimates

A Data Mining Analysis Applied to a Straightening Process Database

peer reviewedThe complexity of modern manufacturing processes in a highly competitive environment forces the manufacturers to invest massively in automation and monitoring systems. The large data flows from these new installations are sources of valuable and hidden knowledge that is so far hardly used. Data mining methods through integrated data analysis tools give a solution to this situation, allowing easy retrieval of knowledge starting from a data base. This is also a unique opportunity to learn faster about the process and to detect hidden and complex relationships between parameters involved. Within this framework we have decided to apply this data analysis method to the straightening process in shipbuilding. We refer to Caprace et al. (2007) for additional illustrations. In shipbuilding, the assembly of elements by welding involves temperature gradients within the ma- terial. These cause deformations which sometimes have to be reduced to obtain an acceptable surface flatness. The straightening process to eliminate these distortions for esthetical or functional reasons is labour intensive. Estimating the straightening impact on the production workload is interesting in the context of production simulation, cost assessment of ship hull, structure optimization, design for production, etc. To reach these objectives, the idea was to elaborate, through a data mining approach, a formula linking the straightening cost to the sections scantlings (plate thickness, dimension and inter-distance of longitudinal stiffeners, dimension and inter-distance of transversal frames) and to other section characteristics. This paper describes each stage of the methodology: data description, analysis of data quality, data exploration and finally choice of discriminatory attributes and the generation of the data-driven models.InterSHI

Analyse par exploration de données afin d'évaluer la charge de travail suplémentaire causée par les déformations de soudage

peer reviewedThis paper presents a way to minimize cost in shipbuilding industry by using the results of a data mining analysis aiming to improve the cost knowledge of the additional operations caused by welding distortions. This statistical analysis had the scope to establish assessment formulas of the supplementary workloads in function of scantlings and welding distortions. Those formulas can be useful to evaluate the profitability of new welding devices and can improve the research in the following domains: production simulation, cost assessment of ship hull, structure optimization, design for production, etc

Mesure floue pour évaluer la productivité du redressage au début du design

peer reviewedSince several years, the large shipyards use more and more thin plates to build up stiffened panels in order to decrease the structural weight. The major problem relating to the utilization of thin plates is the occurrence of welding distortions that have to be eliminated for esthetical and service reasons. This straightening operation involves significant costs and it seems thus important to characterize its economical impact on the global hull fabrication. This paper presents a way to minimize cost in shipbuilding industry by the implementation of a producibility fuzzy metric in order to obtain a better knowledge of the straightening process. Attention has been focused on the definition of fuzzy rules by experts but also on the optimisation of the decision surface to reduce the error compared to actual measurement points

Least cost optimization of a large passenger vessel

peer reviewe

Optimisation de l'allocation de surface appliquée à la prduction de la partie inférieure d'une plateforme semi-submersible

peer reviewedThis paper presents a part of new developments included inside a holistic optimisation strategy during the design cycle of ships. The first part of the paper describes an algorithm to maximize the number of ship blocks and ship sections to produce in workshops during a certain time window. A tool was developed in order to support planners to improve the space utilization and workshop productivity. Thanks to this software, the scheduling is now done more efficiently and above all it takes less time. The second part of the paper describes a recent development of an algorithm able to generate a feasible blocks erection sequence starting from the blocks splitting definition. The idea is to integrate this module as a new functionality inside simulation software in order to take into account blocks sequence during the elaboration of the optimised production strategy. The two developments were validated on the lower hull of a semi-submersible platform coming from a new Brazilian shipyard

La sixième réforme de l’Etat : l’art de ne pas choisir ou l’art du compromis ?

L'ouvrage propose une synthèse pédagogique de la Sixième Réforme de l’Etat, après son entrée en vigueur, autour d’un fil conducteur commun nous conduisant à évaluer juridiquement les choix posés par le législateur et le pouvoir constituant