1,721,163 research outputs found
Matheuristics: using mathematics for heuristic design
Full text linkMatheuristics are heuristic algorithms based on mathematical tools such as the ones provided by mathematical programming, that are structurally general enough to be applied to different problems with little adaptations to their abstract structure. The result can be metaheuristic hybrids having components derived from the mathematical model of the problems of interest, but the mathematical techniques themselves can define general heuristic solution frameworks.
In this paper, we focus our attention on mathematical programming and its contributions to developing effective heuristics. We briefly describe the mathematical tools available and then some matheuristic approaches, reporting some representative examples from the literature. We also take the opportunity to provide some ideas for possible future development
Last‐mile delivery with drone and lockers
Full text linkIn this article, we define a new routing problem that arises in the last-mile delivery of parcels, in which customers can be served either directly at home by a capacitated truck, or possibly with a drone carried on the truck, or in a self-service mode using one of the available lockers. We investigate four different formulations, and for one of them, we propose a branch-and-cut approach. We also discuss some possible variants of the original problem. In the computational experiments, we analyze and compare the performance of the four formulations for the problem and its variants, and we provide some useful managerial insights
An Ant System Heuristic for the Two-Dimensional Finite Bin Packing Problem: preliminary results
No full textRoute relaxations on GPU for vehicle routing problems
No full textState-Space Relaxation (SSR) is an approach often used to compute by dynamic programming (DP) effective bounds for many combinatorial optimization problems. Currently, the most effective exact approaches for solving many Vehicle Routing Problems (VRPs) are DP algorithms making use of SSR for computing their bounding components. In particular, most of these make use of the q-route and ng-route relaxations. The bounding procedures based on these relaxations provide good quality bounds but they are often time consuming to compute, even for moderate size instances. In this paper we investigate the use of GPU computing for solving q-route and ng-route relaxations. The results prove that the proposed GPU implementations are able to achieve remarkable computing time reductions, up to 40 times with respect to the sequential versions
A Fast and Continuous CT scanner for the optimization of logs in a sawmill
Full text linkCT Log is a CT scanner used in an industrial process at very high speed in order to optimize the production of wood boards and other wood products. The scanner can reach 160 m/min, the typical speed at which wood logs are sawn in the sawmills. After the logs pass though the scanner, the images are reconstructed and processed in order to allow the automatic optimization of the cutting pattern according to the constraints set by wood defects and the value of the different products.
Building a a buffer between the scanner and the sawing line is expensive and often not possible because of constraints on the plant layout The time available for the entire processing is therefore very short, because it must be completed before the log reaches the breakdown equipment. In this paper, we present the structure of the scanner and the way we implemented the different stages of processing in order maximize the speed of the elaboration
Matheuristics : survey and synthesis
Full text linkIn integer programming and combinatorial optimisation, people use the term matheuristics to refer to methods that are heuristic in nature, but draw on concepts from the literature on exact methods. We survey the literature on this topic, with a particular emphasis on matheuristics that yield both primal and dual bounds (i.e., upper and lower bounds in the case of a minimisation problem). We also make some comments about possible future developments
Self-adaptive Publish/Subscribe Network Design
No full textThe pub/sub pattern is gaining momentum in IoT architectures, thanks to its robustness and since it offers many-to-many communication. Efficient network management is needed when only scarce and unreliable resources are available as network infrastructure. Moreover, any form of centralized control should be avoided so as not to limit the application potential. This short paper presents preliminary results of a research line casting pub/sub communication as a dynamic network design problem and supporting optimized adaptive routing via a fully distributed Lagrangian matheuristic applied to an extension of the integer multicommodity flow problem
Customer Clustering and Sales Area Design
No full textA common problem in local distribution arises when a company, or an agency in the case of city logistics,
has to plan recurrent delivery and collection activities over a certain, typically urban territory. Goods are
available at one or more warehouses and have to be transported to customers located in the territory,
where reverse logistics operations could also be needed. All customers are registered in the customer
anagraphic of the company ERP and have issued recurrent orders, to be serviced within the planning
period. Visits at the customers must be made on different days, according to feasible, well-spread day
combinations. Moreover, attempted sales could be tried by the vehicle driver along his route. The overall
objective is the minimization of the transportation costs, as resulting from the sum of travel costs of all
routes of the company vehicles during the planning period
Method and apparatus for non-destructive inspection of fruits having an axis of rotational symmetry
Full text linkThis invention relates to a method for non-destructive inspection of a fruit (1) having an axis of rotational symmetry (10). The method comprises the step of positioning the fruit (1) in such a way that its axis of rotational symmetry (10) has an orientation that is substantially parallel to a predetermined plane (20) and the step of radiographing the fruit (1), where the direction of emission of X-rays is substantially perpendicular to said predetermined plane (20) and an X-ray image obtained (41) lies on said predetermined plane (20). The X-ray image obtained (41) is processed to calculate, at corresponding points of the X-ray image (41), respective values of attenuation of the X-ray signal through the fruit (1). The X-ray image (41) is divided into a plurality of sections (415) which are perpendicular to the projection (410) of the axis of rotational symmetry (10) on the predetermined plane (20). Each section (415) is the projection of a corresponding slice of the fruit (1) that is substantially perpendicular to the axis of rotational symmetry (10). For each section (415), the deviation between a signal attenuation trend obtained from processing the X-ray image and a reference trend, or the deviation between a trend of a local coefficient of average attenuation obtained from processing the X-ray image and a trend with constant value, is examined in order to identify any anomalies, discontinuities or variations which are indicative of respective nonuniformities in the corresponding slice of fruit. This invention also relates to an apparatus (9) for carrying out a non-destructive inspection of a fruit (1) having an axis of rotational symmetry (10), said apparatus being configured for implementing the method according to the invention
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