Search results for "Heuristic"
showing 10 items of 476 documents
A branch & bound algorithm for cutting and packing irregularly shaped pieces
2013
Abstract Cutting and packing problems involving irregular shapes, usually known as Nesting Problems, are common in industries ranging from clothing and footwear to furniture and shipbuilding. Research publications on these problems are relatively scarce compared with other cutting and packing problems with rectangular shapes, and are focused mostly on heuristic approaches. In this paper we make a systematic study of the problem and develop an exact Branch & Bound Algorithm. The initial existing mixed integer formulations are reviewed, tested and used as a starting point to develop a new and more efficient formulation. We also study several branching strategies, lower bounds and procedures f…
A problem-adjusted genetic algorithm for flexibility design
2013
Many present markets for goods and services have highly volatile demand due to short life cycles and strong competition in saturated environments. Determination of capacity levels is difficult because capacities often need to be set long before demand realizes. In order to avoid capacity-demand mismatches, operations managers employ mix-flexible resources which allow them to shift excess demands to unused capacities. The Flexibility Design Problem (FDP) models the decision on the optimal configuration of a flexible (manufacturing) network. FDP is a difficult stochastic optimization problem, for which traditional exact approaches are not able to solve but the smallest instances in reasonable…
An Empirical Investigation of Heavy Tails in Emerging Markets and Robust Estimation of the Pareto Tail Index
2021
In this work we analyze and compare the performances of VaR-based estimatorswith respect to three different classes of distributions, i.e., Gaussian, Stable and Pareto, and to different emerging markets, i.e., Egypt, Qatar and Mexico. This is motivated by the evidence that there are points of distinction between emerging and developed markets mainly relating to the speed and reliability of information available to investors.We propose a computational Threshold Accepting-VaR based algorithm (TAVaR) for optimally estimating the Pareto tail index. A Monte Carlo bias estimation analysis is also carried out by comparing our proposed methodology with the Hill estimator and a variant of it.
Mixed heuristic-non linear optimization of energy management for hydrogen storage-based multi carrier hubs
2014
In this paper, an heuristic and non-linear programming based algorithm to optimally operate an energy hub plant is proposed. The energy hub plant described in this work is the test system for the European INGRID research project. The Energy Management System defines the optimal energy flows dispatch in order to obtain the energy balance and the maximum profit for the owner of the plant. The problem is highly constrained and non-linear, for this reason the methodology cannot rely on Linear Programming (LP) methods. The Energy Management System manages two energy carriers, electricity and hydrogen, interfacing three distribution networks: the electricity, the hydrogen and the methane networks…
Integrating usability work into a large inter-organisational agile development project: Tactics developed by usability designers
2015
We examined how usability activities were integrated in a large inter-organisational agile development project.The collaboration between the usability designers and agile team members was affected by the size and nature of the project.Results showed integration was achieved through 5 tactics employed by the usability designers.Three propositions for organising usability activities in agile projects were derived. In this paper we examine the integration of usability activities into a large inter-organisational agile development project. Inter-organisational agile projects possess unique attributes. They involve multiple stakeholders from different organisational contexts and are thus charact…
RutaRep: a computer package to design dispatching routes in the meat industry
2005
In this paper we present a computer program that has been developed to design the dispatching routes of a medium-sized meat company in Spain. We have modelled the real problem as a variant of the vehicle routing problem with Time Windows and implemented a number of heuristic algorithms based on the most advanced solution techniques for this problem. These algorithms have been embedded in a computer package that is intended to be used as a decision support system for the distribution manager. The program runs under Windows System and is straightforward to use. We also present some computational experiences based on real instances provided by the company. This experience shows important impro…
Static and dynamic policies with RFID for the scheduling of retrieval and storage warehouse operations
2013
Warehouses are essential components of logistics and supply chains. The performance of warehouse operations significantly affects the efficiency of the whole chain it belongs to. Radio frequency identification (RFID) is an emerging technology capable of providing real-time information about the location and properties of tagged object(s), such as people, equipment or products. The objective of this article is threefold, to propose and compare different offline and online policies for the scheduling of warehouse operations, to design a tool that allows the decision maker to compare policies and environments without putting them into practice, and to study the benefits that can be obtained if…
Heuristic and Backstepping Control Strategies for Semiactive Suspension in Automotive Systems Equipped with MR Dampers
2010
Abstract This paper deals with the problem of semiactive vibration reduction in a class of automotive systems. Most conventional suspensions use passive devices to absorb impacts and vibrations, which is generally difficult to adapt to the uncertain circumstances. Semiactive suspension techniques promise a solution to the above problem with some comparatively better features than active and passive suspension devices. In this work, the semiactive suspension with magnetorheological (MR) dampers is applied for the vibration attenuation. Both backstepping and heuristic control strategies are proposed. In the design of backstepping controller, the Dahl model of the MR damper is used to estimate…
Sensing and Generating New Opportunities for Value Innovation: How Team Behaviour Contributes to Success or to Failure?
2017
The behavioral side of the decision process inherent to strategy is an issue that is gaining attention from both academic and practitioners. At the same time, the Schumpeterian conception of innovation, returns to gain relevance in an environment where technology leads to process dematerialization and exponential paths of change. In this context, this paper analyses which decision processes, cognitive abilities and heuristics lead to sense and generate value innovation for customers. The analysis of 26 master student teams that ran the same strategy simulator show that the consideration and description of a wide range of alternatives and team agreement as a result of discussion of such alte…
Split-Delivery Capacitated Arc-Routing Problem: Lower Bound and Metaheuristic
2010
International audience; This paper proposes lower and upper bounds for the split-delivery capacitated arc-routing problem (SDCARP), a variant of the capacitated arc-routing problem in which an edge can be serviced by several vehicles. Recent papers on related problems in node routing have shown that this policy can bring significant savings. It is also more realistic in applications such as urban refuse collection, where a vehicle can become full in the middle of a street segment. This work presents the first lower bound for the SDCARP, computed with a cutting plane algorithm and an evolutionary local search reinforced by a multistart procedure and a variable neighborhood descent. Tests on …