Stefan Voβ

Applying the corridor method to a blocks relocation problem

In this paper, we present a corridor method inspired algorithm for a blocks relocation problem in block stacking systems. Typical applications of such problem are found in the stacking of container terminals in a yard, of pallets and boxes in a warehouse, etc. The proposed algorithm applies a recently proposed metaheuristic. In a method-based neighborhood we define a two-dimensional “corridor” around the incumbent blocks configuration by imposing exogenous constraints on the solution space of the problem and apply a dynamic programming algorithm capturing the state of the system after each block movement for exploring the neighborhoods. Computational results on medium- and large-size problem instances allow to draw conclusions about the effectiveness of the proposed scheme.

Efficiency considerations for sequencing and scheduling of double-rail-mounted gantry cranes at maritime container terminals

The current decade has seen a considerable growth in worldwide container transportation and with it, an indispensable need for optimisation. This paper seeks to investigate to which extent double-rail-mounted gantry cranes can help to improve a container terminals efficiency. A simulation study is conducted for evaluating different online algorithms for sequencing and scheduling of jobs for automated double-rail-mounted gantry cranes serving a terminals storage block. The experiments are based upon scenarios that are derived from the real world (Container Terminal Altenwerder, CTA, Hamburg, Germany) in order to investigate advantages as well as problems and limits of our algorithms and the specific crane systems. Furthermore, the influence of the horizontal transport at the blocks interfaces is examined.

Dispatching of an Electric Monorail System: Applying Metaheuristics to an Online Pickup and Delivery Problem

In this article we present a new solution approach for a specific online pickup and delivery problem as it occurs in a real-world dispatching task of electric monorail load carriers. The presented optimization module adapts the communication structure of the respective IT components of the warehouse system to facilitate an easy integration. Numerical results are presented comparing steepest descent as well as reactive tabu search and simulated annealing with the dispatching system used so far. Tests are performed on the basis of a detailed simulation model of the entire warehouse and show a clear superiority for this approach.

Vehicle Routing Problems and Container Terminal Operations - An Update of Research

Containers came into the market for international conveyance of sea freight almost five decades ago. The breakthrough was achieved with large investments in specially designed ships, adapted seaport terminals with suitable equipment, and availability of containers. Today over 60 % of the world’s deep-sea general cargo is transported in containers and some routes are even containerized up to 100 %. Seaport container terminals face a high demand for advanced optimization methods. A crucial competitive advantage is the rapid turnover of the containers, which corresponds to an efficient handling of containers as well as to a decrease of the costs of the transshipment processes. One of the key concerns in this respect refers to various types of equipment at container terminals devoted to the routing of containers to achieve high productivity. For instance, a variety of vehicles is used for the horizontal transport at the quayside and at the landside.

POPMUSIC as a matheuristic for the berth allocation problem

The Berth Allocation Problem aims at assigning and scheduling incoming vessels to berthing positions along the quay of a container terminal. This problem is a well-known optimization problem within maritime shipping. In order to address it, we propose two POPMUSIC (Partial Optimization Metaheuristic Under Special Intensification Conditions) approaches that incorporate an existing mathematical programming formulation. POPMUSIC is an efficient metaheuristic that may serve as blueprint for matheuristics approaches once hybridized with mathematical programming. In this regard, the use of exact methods for solving the sub-problems defined in the POPMUSIC template highlight an interoperation between metaheuristics and mathematical programming techniques, which provide a new type of approach for this problem. The computational experiments reveal excellent results.

An improved formulation for the multi-depot open vehicle routing problem

The multi-depot open vehicle routing problem (MDOVRP) is a recent hard combinatorial optimization problem that belongs to the vehicle routing problem family. In the MDOVRP, the vehicles depart from several depots and once they have delivered the goods to the last customers in their routes they are not required to return to the depots. In this work, we propose a new mixed integer programming formulation for the MDOVRP by improving some constraints from the literature and proposing new ones. The computational experience carried out over problem instances from the literature indicates that our proposed model outperforms the existing one.

A hybridized tabu search approach for the minimum weight vertex cover problem

The minimum weight vertex cover problem is a basic combinatorial optimization problem defined as follows. Given an undirected graph and positive weights for all vertices the objective is to determine a subset of the vertices which covers all edges such that the sum of the related cost values is minimized. In this paper we apply a modified reactive tabu search approach for solving the problem. While the initial concept of reactive tabu search involves a random walk we propose to replace this random walk by a controlled simulated annealing. Numerical results are presented outperforming previous metaheuristic approaches in most cases.

Information systems in seaports: a categorization and overview

Information systems have become indispensable to the competitiveness of ports, facilitating communication and decision making for enhancing the visibility, efficiency, reliability, and security in port operations under various conditions. Providing value-added information services and analytics is increasingly important to maintain a competitive edge and to fulfill regulatory requirements. Consequently, it is necessary to survey current information systems both from an academic and practical standpoint. In this paper, we present a classification and a comprehensive survey of information systems and related information technologies applied in ports. As such, the paper provides a state-of-the-art information-centric view on port operations and aims to bridge the gap between industry solutions and academic works.

A math-heuristic Dantzig-Wolfe algorithm for capacitated lot sizing

The multi-item multi-period capacitated lot sizing problem with setups (CLST) is a well known optimization problem with wide applicability in real-world production planning problems. Based on a recently proposed Dantzig-Wolfe approach we present a novel math-heuristic algorithm for the CLST. The major contribution of this paper lies in the presentation of an algorithm that exploits exact techniques (Dantzig-Wolfe) in a metaheuristic fashion, in line with the novel trend of math-heuristic algorithms. To the best of the authors’ knowledge, it is the first time that such technique is employed within a metaheuristic framework, with the aim of tackling challenging instances in short computational time. Moreover, we provide reasoning that the approach may be beneficial when additional constraints like perishability constraints are added. This also constitutes an important extension when looking at it from the view of solution methods.

Special issue on mathematical contributions to metaheuristics editorial

Using mathematical models in the framework of heuristic algorithms is no news in applied computer science if we consider, for instance, the development of linear programming to assist with the scheduling of the airlift during the Berlin blockade right after World War II. Similar applications, though possibly not with such grand results, have been developed ever since. So, why this special issue, primarily meant for putting an emphasis on the possibility of embedding sound mathematical techniques into robust algorithmic approaches to optimization? The reason is twofold. First, the literature has demonstrated the possibility of using extremely effective algorithmic schemes, namely metaheuristics, for solving hard optimization problems. However, current metaheuristics make no use of explicit mathematical tools. Second, innovative mathematical tools have been proposed, refined and shown quite effective on optimization problems that are combinatorial, stochastic or continuous in nature. These tools, however, target the exact solution of these problems. The use of mathematics in heuristics design, and most notably in metaheuristics design, has been largely neglected in the optimization literature and more generally by the optimization community. For example, in the last installment of the Meta-