Zellen des Immunsystems: vom Polarkreis ins All

Zusammenfassung: Das Immunsystem gehört auf einem Raumflug zu den am stärksten beeinträchtigten Systemen des menschlichen Körpers. Die Ursache dieser Störung liegt wahrscheinlich auf Ebene der Zellen. Experimente an Bord einer TEXUS-Forschungsrakete sollen nun Aufschluss hierüber gebe

Simulation ausgewählter Heuristiken zur Tourenplanung in manuellen Kommissionierstationen

Im Folgenden werden die Auswirkungen des Einsatzes verschiedener Heuristiken zur Tourenplanung in manuellen Kommissionierstationen bei einem Pharmagroßhandel untersucht. Dabei wird nicht nur auf die Läange der Touren eingegangen, sondern zusätzlich die Auswirkung von Ressourcenkonflikten während der Kommissionierung auf die Dauer der Bedienzeiten betrachtet. Nach einer Beschreibung des Systems werden dazu zuerst der Entwurf und die Implementierung eines agentenbasierten Modells dargestellt. Daraufhin werden einige häufig verwendete Heuristiken eingeführt und für den Anwendungsfall evaluiert. Am Schluss steht eine kurze Zusammenfassung und ein Ausblick auf das weitere Vorgehen

Theoretical and Experimental Investigations on the Recirculation of the Solution (Mix-Flow) in an Absorption Resorption Refrigeration System

Ammonia water absorption resorption refrigeration systems do not need a rectification column like conventional absorption refrigeration systems do. In this case such systems need a recirculation of the solution. This so called “mix flow” is necessary to prevent the dilution of the solution in the “cold cycle” of the system which is caused by the relative high concentration of water in the hot vapor. The influence of this recirculation of the solution on the performance of the system could be shown in previous studies and is now modelled and investigated more in detail. As a result of the theoretical investigation, a preferred internal piping layout, especially for the mix flow pipe, is proposed. In addition, the theoretical foundations are verified with extended experimental investigations at an existing test cycle

A robust schedule for Montpellier's Tramway network

The city of Montpellier in the Languedoc-Roussillon region of France features a fast growing tram network as a central part of its public service infrastructure. Here, as in many other tram networks, resources like tracks and stations are shared between different lines. Because of the resulting dependencies, small inevitable delays can spread through the network and affect its global performance. Abstract This article examines whether a robust tram schedule may help to raise punctuality in Montpellier's tram network. To accomplish this, we apply a tool set designed to generate schedules optimized for robustness, which also satisfy given sets of planning requirements. These tools allow to compare time tables with respect to their punctuality and other key indicators. Abstract After an introduction to the goals of this paper, we continue with a description of the tool set focusing on optimization and simulation modules. These software utilities are then employed to generate and simulate robust and non-robust schedules for Montpellier's tram network, which are subsequently compared for the resulting delays

Model-based parallelization of discrete traffic simulation models

To re-establish regular operations in a tram traffic network after a large disturbance, e.g. resulting from vehicle breakdown or station closure, the viability of several rescheduling and rerouting strategies has to be evaluated prior to their implementation. Here, a multi-modal traffic simulation system can help to enhance the decision quality. Such a system obviously faces tight time constraints, so simulation data has to be acquired fast. In this paper we propose a method for the parallel execution of discrete traffic simulation models, which would accelerate data generation in comparison to a sequential model. To assess this method's dynamic behavior in real-world applications, some experiments conducted on a software system modeling schedule based tram traffic are presented. After giving an introduction to the scope and aim, we show some background on the parallelization of discrete simulation models. The main part of the paper begins with the proposal of a method to parallelize the execution of simulation models with problem specific properties. Some estimations of the method's efficiency are shared, followed by several experiments to highlight its dynamic behavior in real-world applications. The paper ends with a short summary and some thoughts on further research

Reducing blocking effects in multi-block layouts

Tour planning in multi-block layouts is a common exercise in logistics. In those systems, blocking effects result from conflicting agents competing for resources. Although clearly exceptional in real world applications, most methods of tour planning assume only one active agent, and thus do not consider blocking effects. In this paper we examine heuristic methods of tour planning in multi-block layouts with multiple agents, finding that blocking effects have a significant impact on system performance. We show that methods devised for the mentioned special case do not scale very well when applied to scenarios with multiple agents. We propose a heuristic method which is capable of reducing blocking effects. It generates tours of equal or shorter length than those produced by the other examined methods

Reduzieren robuste Fahrpläne Verspätungen in Stadtbahnnetzen? - Es kommt drauf an!

Nicht in jedem Stadtbahnnetz ist Robustheit als Optimierungskriterium für Fahrpläne gleich-sam geeignet. Im Rahmen dieses Beitrags werden deshalb Faktoren für die Netzstruktur bestimmt, die die Wirksamkeit von Robustheit als verspätungsmindernden Faktor beeinflus-sen. Anhand von Optimierungs- und Simulationsexperimenten auf Basis von Modellen der Stadtbahnnetze von Köln und Montpellier werden die definierten Einflussfaktoren getestet

Modeling time table based tram traffic

In mid-sized cities, tram networks are major components of public service infrastructure. In those networks with their typically dense schedules, multiple lines share tracks and stations, resulting in a dynamic system behavior and mounting delays following even small disruptions. Robustness is an important factor to keep delays from spreading through the network and to minimize average delays. This paper describes part of a project on simulation and optimization of tram schedules, namely the devel-opment and application of a simulation model representing a tram network and its assigned time table. We begin by describing the components of a tram network, which consist of physical and logical entities. These concepts are then integrated into a model of time table based tram traffic. We apply the resulting simulation software to our hometown Cologne's tram network and present some experimental results