Showing papers by "Malte Fliedner published in 2013"
TL;DR: This paper reviews container processing in railway yards from an operational research perspective and analyzes basic decision problems for the two most important yard types, namely conventional rail-road and modern rail-rail transshipment yards.
Abstract: In spite of extraordinary support programs initiated by the European Union and other national authorities, the percentage of overall freight traffic moved by train is in steady decline. This development has occurred because the macroeconomic benefits of rail traffic, such as the relief of overloaded road networks and reduced environmental impacts, are counterbalanced by severe disadvantages from the perspective of the shipper, e.g., low average delivery speed and general lack of reliability. Attracting a higher share of freight traffic on rail requires freight handling in railway yards that is more efficient, which includes technical innovations as well as the development of suitable decision support systems. This paper reviews container processing in railway yards from an operations research perspective and analyzes basic decision problems for the two most important yard types: conventional rail--road and modern rail--rail transshipment yards. Furthermore, we review the relevant literature and identify open research challenges.
110 citations
TL;DR: The assembly line balancing problem is modified by modeling setups more realistically, a new, more compact mathematical model formulation is given and effective heuristic solution procedures are developed that outperform formerly proposed heuristics.
Abstract: Assembly line balancing problems (ALBP) consist of distributing the total workload for manufacturing any unit of the products to be assembled among the work stations along a manufacturing line as used in the automotive or the electronics industries. Usually, theory assumes that, within each station, tasks can be executed in an arbitrary precedence-feasible sequence without changing station times. In practice, however, the task sequence may influence the station time considerably as sequence-dependent setups (e.g., walking distances, tool changes) have to be considered. Including this aspect leads to a joint balancing and scheduling problem, which we call SUALBSP (setup assembly line balancing and scheduling problem). In this paper, we modify the problem by modeling setups more realistically, give a new, more compact mathematical model formulation and develop effective heuristic solution procedures. Computational experiments based on existing and new data sets indicate that the new procedures outperform formerly proposed heuristics. They are able to solve problem instances of real-world size with small deviations from optimality in computation times short enough to be accepted in real-world decision support systems.
70 citations
TL;DR: In this article, a new class of single-machine scheduling problems, which are faced by Just-in-Time suppliers satisfying a given demand, is studied, where the processing of jobs leads to a release of a predefined number of product units into inventory.
Abstract: This paper studies a new class of single-machine scheduling problems, which are faced by Just-in-Time-suppliers satisfying a given demand. In these models the processing of jobs leads to a release of a predefined number of product units into inventory. Consumption is triggered by predetermined time-varying, and product-specific demand requests. While all demands have to be fulfilled, the objective is to minimize the resulting product inventory. We investigate different subproblems of this general setting with regard to their computational complexity. For more restricted problem versions strongly polynomial time algorithms are presented. In contrast to this, NP-hardness in the strong sense is proven for more general problem versions. Moreover, for the most general version, even finding a feasible solution is shown to be strongly NP-hard.
17 citations
TL;DR: In this article, the authors consider a scheduling problem occurring in the hinterland of many medium-sized container ports, where containers from a storage yard need to be loaded onto freight trains by straddle carriers (SCs).
Abstract: This paper considers a scheduling problem occurring in the hinterland of many medium-sized container ports. Here, containers from a storage yard need to be loaded onto freight trains by straddle carriers (SCs). The main complicating fact in the resulting train loading problem with straddle carriers (TLSC) is that the track provides only one-sided access and while straddling the train SCs cannot pass each other. This paper introduces the TLSC with two different policies to avoid obstructions of SCs in the track lane, settles computational complexity, and compares both policies in a comprehensive computational study.
6 citations