FEMM - Working Paper Series - 2022


Working Paper Series auf der OVGU-Journals-Plattform


Julia Zimmermann

On the design of a flow line with intermediate buffers and mixed corrective maintenance


We considered a mixed corrective maintenance policy for machines in a two-machine one-buffer flow line. The machines had stochastic processing times and suffered from unexpected failures. In the case of a failure, the machines were either minimally repaired or their failing components were replaced by spare parts. While the replacement strategy is rapid and the system can be considered new thereafter, spare parts provisioning and storage costs are very high. Thus, we additionally considered minimal repairs, which are less expensive and restore the system to a working condition at a minimum. We modeled the system as a continuous-time Markov chain. This approach was used to measure the performance of the flow line and the mixed corrective maintenance policy employed. To facilitate design decisions for the flow line, we considered both the cost of an interstage buffer and the maintenance costs for machines in line. We formulated an optimization problem based on a profit function that enables the simultaneous optimization of the buffer size and maintenance strategy. Our numerical analyses reveal useful insights into the performance and optimal design of the flow line depending on the utilized maintenance strategy.

Keywords: flow line, buffer, spare parts, mixed corrective maintenance


Jarmo Haferkamp/Marlin Wolf Ulmer/Jan Fabian Ehmke

Heatmap-based Decision Support for Repositioning in Ride-Sharing Systems


In ride-sharing systems, platform providers aim to distribute the drivers in the city to meet current and potential future demand and to avoid service cancellations. Ensuring such distribution is particularly challenging in the case of a crowdsourced fleet, as drivers are not centrally controlled but are free to decide where to reposition when idle. Thus, providers look for alternative ways to ensure a vehicle distribution that benefits both users and drivers, and consequently the provider. We propose an intuitive means to improve idle ride-sharing vehicles' repositioning: repositioning opportunity heatmaps. These heatmaps highlight driver-specific earning opportunities approximated based on the expected future demand, fleet distribution, and location of the specific driver. Based on the heatmaps, drivers make decentralized yet better-informed repositioning decisions. As our heatmap policy changes the driver distribution, we propose an adaptive learning algorithm for designing our heatmaps in large-scale ride-sharing systems. We simulate the system and generate heatmaps based on previously learned repositioning opportunities in every iteration. We then update these based on the simulation's outcome and use the updated values in the next iteration. We test our heatmap design in a comprehensive case study on New York ride-sharing data. We show that carefully designed heatmaps reduce service cancellations therefore revenue loss for platform and drivers significantly.

Keywords: mobility-on-demand, vehicle repositioning, crowdsourced transportation, heatmap, stochastic dynamic decision making, adaptive learning


Dr. Dirk Betz/Dr. Claudia Biniossek/Harald Wypior/Dr. Claus-Peter Klas/Narges Tavakolpoursaleh

Metadata Schema x-econ Repository


Since May 2017, the x-hub project partners OVGU Magdeburg, University of Vienna, and GESIS dispose of a new repository, called x-econ (https://x-econ.org). The service is dedicated to all experimental economics research projects to disseminate user-friendly archiving and provision of experimental economics research data.
The repository x-econ contains all necessary core functionalities of a modern repository and is in a continuous optimization process aiming at functionality enhancement and improvement. x-econ is also one pillar of the multidisciplinary repository x-science (https://x-science.org).
The present documentation, which is primarily based on the GESIS Technical Reports on datorium 2014|03 and da|ra 4.0, lists and explains the metadata elements, used to describe research information.



Barbara Schöndube-Pirchegger

Internal and External Information System Choices and Mutual Interdependencies


In this paper, we consider a one shot principal agent problem. The owner of the firm (principal) hires a manager (agent). As firm value is non‐contractible by assumption, an incentive contract is written on accounting income. The manager performs some productive task that increases firm value as well as income but can also engage in earnings management to increase income only.
The owner needs to make several simultaneous choices. First, he needs to decide whether to implement an internal information system (IIS). Second, he has to choose from a set of (external) financial reporting systems that differ with regard to accounting discretion. Third, he needs to specify contracting details.
If an internal information system is implemented it provides the manager with private information about the business environment, which, in turn, affects effort costs. In contrast, the financial reporting system choice affects the effectivity of earnings management activities undertaken by the manager.
In the absence of an internal information system, the agency problem considered is a moral hazard problem that arises from private effort choices of the manager. Implementing an internal information system creates an adverse selection problem on top of the moral hazard problem.
We find that for both problems agency costs increase if the business environment becomes more volatile.
Holding either the IIS choice or the accounting system choice constant, we observe the following: Without an IIS, it is optimal to choose the least discretionary accounting system available. With an IIS it can either be advisable to choose the most or least discretionary accounting system depending on the probability distribution of business environments to be present.
For any given accounting system, the principal implements an IIS if the volatility of the business environment is sufficiently high and v.v. The less discretionary the accounting system, however, the more volatile the business environment needs to be for an IIS to become favorable.
It follows that both, accounting system and IIS choice, are mutually interdependent. E.g. it might be optimal for the principal to choose the most discretionary accounting system along with implementing an IIS. In contrast, it might be optimal not to implement an IIS along with the least discretionary accounting system depending on parameter values.


Letzte Änderung: 02.03.2022 - Ansprechpartner: Webmaster