Routing and scheduling of vehicles and crews: The state of the art

We propose an algorithmic framework that successfully addresses three vehicle routing problems: the multidepot VRP, the periodic VRP, and the multidepot periodic VRP with capacitated vehicles and constrained route duration. The metaheuristic combines the exploration breadth of population-based evolutionary search, the aggressive-improvement capabilities of neighborhood-based metaheuristics, and advanced population-diversity management schemes. Extensive computational experiments show that the method performs impressively in terms of computational efficiency and solution quality, identifying either the best known solutions, including the optimal ones, or new best solutions for all currently available benchmark instances for the three problem classes. The proposed method also proves extremely competitive for the capacitated VRP.

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A Hybrid Genetic Algorithm for Multidepot and Periodic Vehicle Routing Problems

We have witnessed recently the development of a fast growing body of research focused on vehicle routing and scheduling problem structures with time window constraints. It is the aim of this paper to survey the significant advances made for the following classes of routing problems with time windows: the single and multiple traveling salesman problem, the shortest path problem, the minimum spanning tree problem, the generic vehicle routing problem, the pickup and delivery problem including the dial-a-ride problem, the multiperiod vehicle routing problem and the shoreline problem. Having surveyed the state-of-the-art in this area, we then offer some perspectives on future research.

Survey Paper—Time Window Constrained Routing and Scheduling Problems

In the network design problem we are given a weighted undirected graph. We wish to find a subgraph which connects all the original vertices and minimizes the sum of the shortest path weights between all vertex pairs, subject to a budget constraint on the sum of its edge weights. In this note we establish NP-completeness for the network design problem, even for the simple case where all edge weights are equal and the budget restricts the choice to spanning trees. This result justifies the development of enumerative optimization methods and of approximation algorithms, such as those described in a recent paper by R. Dionne and M. Florian.

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The complexity of the network design problem

Recognizing that empirical research into classroom dialogue has been conducted for about 40 years, a review is reported of 225 studies published between 1972 and 2011. The studies were identified through systematic search of electronic databases and scrutiny of publication reference lists. They focus on classroom dialogue in primary and secondary classrooms, covering the full age range of compulsory schooling. The methods of data collection and analysis used in the studies are described and discussed, with changes and continuities over time highlighted. Study results are then summarized and integrated to present a succinct picture of what is currently known and where future research might profitably be directed. One key message is that much more is known about how classroom dialogue is organized than about whether certain modes of organization are more beneficial than others. Moreover, epistemological and methodological change may be required if the situation is to be remedied.

Classroom dialogue: a systematic review across four decades of research

This paper examines a routing design problem in which the objective is to assign customer demand points to days of the week in order to solve the resulting node routing problems over the entire week most effectively. The emphasis is on obtaining approximate solutions for this type of combinatorial problem. Several heuristics are developed and tested on a large scale refuse collection problem. Computational results, as well as a discussion of expected benefits, are presented.

W. Igo

Papers

An assignment routing problem