Arbeitspapier / Research Paper, Lehrstuhl für Betriebswirtschaftslehre, insbes. Logistik-Management

The flexible job shop scheduling problem (FJSSP) is a generalization and extension of the classical job shop scheduling problem (JSSP) in which — prior to the sequencing of operations — an assignment of operations to machines is necessary. In this technical report, we are examining common instances for different specifications of the FJSSP. Furthermore, a new FJSSP specification is introduced, where similar machines are pooled to work centers, and the first and last work center are obligatory. For this practice-oriented problem specification new test instances are presented.

This document presents a simple extension of the TSPLIB file format to serve our needs in the Inventory Routing Problem types. Instead of creating a new file format or putting ASCII files online with a simple description, we have chosen to extend the TSPLIB file format.

One critical problem in wireless sensor networks is to assemble the sensors in different covers in order to solve different objectives such as maximum duration of the network lifetime of minimizing the coverage breach. The output of these problems is a set of covers with a duration of usage. Another problem coming just after is how to schedule the covers. Most of the time, this part is left unsolved as the challenges appear less important than generating the covers. Our current work will describe the wireless sensor network cover scheduling problem (WSN- CSP), a non-linear mathematical model, a MILP model and a heuristic (CSH) that solves this problem. To improve the quality of the solutions, we also propose a memetic algorithm (CSMA). Both approaches will be tested on a large set of instances. Moreover, some complexity results and theorical properties are also given in the paper.

Previous research in the single machine total weighted tardiness problem (SMTWTP) has led to the proposition of effective local search strategies. At least existing benchmark instances from the literature do not pose a challenge for state-of-the-art algorithms. --- This paper describes the proposition of two classes of novel instances for the single machine total weighted tardiness problem. In response to preceding research, they are larger, thus harder to search by local search algorithms. Besides, they are computed w.r.t. control parameters that lead to comparable difficult data sets. --- In addition to providing novel instances, we report best known results, which have been computed by a Variable Neighborhood Descent algorithm.