445 research outputs found
The value of reliability in freight transport : an inventory theoretic approach for guiding managerial decision and analyzing empirical data
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The heterogeneous vehicle routing problem with intermediate storage facilities: a case study from the construction industry
No full textWholesalers of construction materials often need to transport large amounts of materials and heavy equipment from their depots to different construction sites and retail shops using a heterogeneous fleet of vehicles with limited sizes, different transportation capacities and vehicle configurations. Motivated by the case of a large construction wholesaler in the Netherlands, we consider a heterogeneous vehicle routing problem where there are intermediate storage facilities available for material transshipment and temporary storage. This research focuses on formulating the operational requirements, and analyzing the impact of storage facilities on vehicle utilization and routing strategies. The problem is formulated as a mixed integer programming model and solved efficiently using a metaheuristic. Computational results are presented on benchmark instances and real-life problem data
Effective speeding up strategies for tabu search heuristics
No full textTabu search metaheuristics have been developed for decades, making them one of the most widely applied metaheuristic frameworks. Although a standard tabu search framework can offer interesting performance, the effectiveness of a tabu search metaheuristic can be strongly improved by specific implementation features and speed-up strategies that are often overlooked in standard implementations. This presentation discusses a number of speed-up strategies and provides computational results on their effectiveness
ORBEL 15: Fifteenth Belgian Conference on Quantitative Methods and Decision Making: books of abstracts
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An Efficient Implementation of a Static Move Descriptor-based Local Search Heuristic
Full text linkThis paper proposes several strategies for a more efficient implementation of the concept of Static Move Descriptors (SMDs), a recently developed technique that significantly speeds up Local Search-based algorithms. SMDs exploit the fact that each local search step affects only a small part of the solution and allow for efficient tracking of changes at each iteration, such that unnecessary reevaluations can be avoided. The concept is highly effective at reducing computation times and is sufficiently generic to be applied in any Local Search-based algorithm. Despite its significant advantages, the design proposed in the literature suffers from high overhead and high implementational complexity. Our proposals lead to a much leaner and simpler implementation that offers better extendibility and significant further speedups of local search algorithms. We compare implementations for the Capacitated Vehicle Routing Problem (CVRP) - a well-studied, complex problem that serves as a benchmark for a wide variety of optimization techniques
Monetary values of freight transport quality attributes: a sample of Tanzanian firms
No full textThis paper presents the findings of a stated preference research conducted in Tanzania (East Africa). The objective of the survey was to determine the relative importance as well as monetary values attached to freight transport quality attribute by shippers in this region. In-depth interviews with the logistic managers of companies that produce and ship goods were conducted. The freight transport quality attributes considered in this survey were flexibility, frequency, loss and damage, reliability, and transit time. The monetary values of these attributes have been computed as willingness to pay for their improvement as well as willingness to accept compensation for a decrease in their quality. The results show that shippers in this region consider travel time, loss and damage and frequency as the most important quality attributes. This may have relevant implications for the infrastructural transport policies to be implemented in the country
Revisiting service level measurement for an inventory system with different transport modes
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