Search results for " operations"

New trends in manufacturing processes research

2019

Research on manufacturing processes is further enriched and becomes stronger at the 47th North American Manufacturing Research Conference (NAMRC 47) at Penn State University, The Behrend College, Erie, Pennsylvania USA. Innovation is fundamentally connected to products or processes: the former being rarer and more difficult to be obtained, the latter is definitively related to economy, competitiveness and welfare of a nation. Furthermore, the research and success in innovation of processes permit also the proposition of innovative products. Manufacturing processes engineering is of primary interest for industries and new challenges are faced every day in order to reduce costs, increase comp…

Latest developments in manufacturing processes at NAMRC 45

2017

Manufacturing processes are tightly connected to innovation.They have been the key areas that support and influence a nation’scompetitiveness and economy since the eighteenth century. Asthe primary driving force behind economic growth, manufactur-ing processes enable and facilitate innovative products realization,ranging from heavy-duty machinery to hi-tech home electronics.In the past centuries, they have contributed significantly to moderncivilization and created the momentum that drives today’s econ-omy. Despite various achievements in manufacturing processes, weare still facing challenges due to growing complexity in manufac-turing operations, introduction of new manufacturing technolog…

Ultrasonic phased array inspection of wire plus arc additive manufacture samples using conventional and total focusing method imaging approaches

2019

In this study, three aluminium samples produced by wire + arc additive manufacture (WAAM) are inspected using ultrasonic phased array technology. Artificial defects are machined using a centre drill, ø 3 mm, and electrical discharge machining (EDM), ø 0.5-1 mm, in a cylindrical through-hole topology. The samples are first inspected using a single-element wheel probe mounted on a KUKA robot in order to investigate the feasibility of using a conventional ultrasonic transducer approach. Unfortunately, the wheel probe is found to be unsuitable for scanning the WAAM specimens and ultrasonic phased arrays are employed next. The set-up includes 5 MHz and 10 MHz arrays (128 elements) in direct cont…

Energy of dendritic avalanches in thin-film superconductors

2018

A method for calculating stored magnetic energy in a thin superconducting film based on quantitative magneto-optical imaging is developed. Energy and magnetic moment are determined with these calculations for full hysteresis loops in a thin film of the superconductor NbN. Huge losses in energy are observed when dendritic avalanches occur. Magnetic energy, magnetic moment, sheet current and magnetic flux distributions, all extracted from the same calibrated magneto-optical images, are analyzed and discussed. Dissipated energy and the loss in moment when dendritic avalanches occur are related to each other. Calculating these losses for specific spatially-resolved flux avalanches is a great ad…

On Constraint Handling in Surrogate-Assisted Evolutionary Many-Objective Optimization

2016

Surrogate-assisted evolutionary multiobjective optimization algorithms are often used to solve computationally expensive problems. But their efficacy on handling constrained optimization problems having more than three objectives has not been widely studied. Particularly the issue of how feasible and infeasible solutions are handled in generating a data set for training a surrogate has not received much attention. In this paper, we use a recently proposed Kriging-assisted evolutionary algorithm for many-objective optimization and investigate the effect of infeasible solutions on the performance of the surrogates. We assume that constraint functions are computationally inexpensive and consid…

A multistage heuristic for storage and retrieval problems in a warehouse with random storage

2017

The warehouse is one of the essential components of logistics and supply chains. The efficiency of the whole chain is affected by the performance of warehouse operations and, more particularly, the storage and retrieval of goods. This paper considers a storage and retrieval problem in a real warehouse with random storage and different types of forklifts, depending on the locations they can access. The problem deals with selecting locations to store/retrieve a predefined set of pallets, assigning an adequately skilled forklift to each operation and determining the order in which each forklift will perform its operations so that the total employed time is minimized. The problem is solved heur…

A parallel variable neighborhood search approach for the obnoxious p -median problem

2018

Interactive Multiobjective Robust Optimization with NIMBUS

2018

In this paper, we introduce the MuRO-NIMBUS method for solving multiobjective optimization problems with uncertain parameters. The concept of set-based minmax robust Pareto optimality is utilized to tackle the uncertainty in the problems. We separate the solution process into two stages: the pre-decision making stage and the decision making stage. We consider the decision maker’s preferences in the nominal case, i.e., with the most typical or undisturbed values of the uncertain parameters. At the same time, the decision maker is informed about the objective function values in the worst case to support her/him to make an informed decision. To help the decision maker to understand the behavio…

A genetic algorithm for the minimum generating set problem

2016

Graphical abstractDisplay Omitted HighlightsWe propose a novel formulation for the MGS problem based on multiple knapsack.The so-conceived MGS problem is solved by a novel GA.The GA embeds an intelligent construction method and specialized crossover operators.We perform a thorough comparison with regards to state-of-the-art algorithms.The proposal proves to be very competitive, specially for large and hard instances. Given a set of positive integers S, the minimum generating set problem consists in finding a set of positive integers T with a minimum cardinality such that every element of S can be expressed as the sum of a subset of elements in T. It constitutes a natural problem in combinat…

On the sure criticality of tasks in activity networks with imprecise durations

2002

BB; International audience; The notion of the necessary criticality (both with respect to path and to activity) of a network with imprecisely defined (by means of intervals or fuzzy intervals) activity duration times is introduced and analyzed. It is shown, in the interval case, that both the problem of asserting whether a given path is necessarily critical and the problem of determining an arbitrary necessarily critical path (more exactly, a subnetwork covering all the necessarily critical. paths) are easy. The corresponding solution algorithms are proposed. However, the problem. of evaluating whether a given activity is necessarily critical does not seem to be such. Certain conditions are…