State of the Art Overview on Automatic Railway Timetable Generation and Optimization

In railway transportation, each train needs to have a timetable that specifies which track at which time will be occupied by it. This task can be addressed by automatization techniques both in generating a timetable and in optimizing an existing one. In this paper, we give an overview on the state of the art of these techniques. We study the computation of a technically valid slot for a train that guarantees a (short) spatial and temporal way through the network. Furthermore, the construction of a cyclic timetable where trains operate e.g. every 60 minutes, and the simultaneous construction of timetables for multiple trains are considered in this paper. Finally, timetables also need to be robust against minor delays. We will review the state of the art in the literature for these aspects of railway timetabling with respect to models, solution algorithms, complexity results and applications in practice

Railway Timetable Optimization

In this cumulative dissertation, we study several aspects of railway timetable optimization. The first contributions cover Practical Applications of Automatic Railway Timetabling. In particular, for the problem of simultaneously scheduling all freight trains in Germany such that there are no conflicts between them, we propose a novel column generation approach. Each train can choose from an iteratively growing set of possible routes and times, so called slots. For the task of choosing maximally many slots without conflicts, we present and apply the heuristic algorithm Conflict Resolving (CR). With these two methods, we are able to schedule more than 5000 trains simultaneously, exceeding the scopes of other studies. A second practical application that we study is measuring the capacity increase in the railway network when equipping freight trains with electro-pneumatic brakes and middle buffer couplings. Methodically, we propose to explicitly construct as many slots as possible for such trains and measure the capacity as the number of constructed slots. Furthermore, we contribute to the field of Algorithms and Computability in Timetable Generation. We present two heuristic solution algorithms for the Maximum Satisfiability Problem (MaxSAT). In the literature, it has been proposed to encode different NP-complete problems that occur in railway timetabling in MaxSAT. In numerical experiments, we prove that our algorithms are competitive to state-of-the-art MaxSAT solvers. Moreover, we study the parameterized complexity status of periodic scheduling and give proofs that the problem is NP-complete for input graphs of bounded treewidth, branchwidth and carvingwidth. Finally, we propose a framework for analyzing Delay Propagation in Railway Networks. More precisely, we develop delay transmission rules based on different correlation measures that can be derived from historical operations data. What is more, we apply SHAP values from Explainable AI to the problem of discerning primary delays that occur stochastically in the operations, to secondary follow-up delays. Transmission rules that are derived from the secondary delays indicate where timetable adjustments are needed. In our last contribution in this field, we apply such adjustment rules for black-box optimization of timetables in a simulation environment

Modeling Delay Propagation and Transmission in Railway Networks

In railway scheduling, the planning of time supplements is crucial to the robustness of the resulting timetable. Time supplements as a means to accommodate for train delays are often distributed according to operation rules and based on experience. A part of the project for strategic schedule optimization at DB Netze aims at improving the supplements distribution through learning of structures of delay propagation and transmission from historical railway operation data. The work at hand focuses on delay transmissions between trains. It employs correlations and correlation network analysis to identify and analyze these knock-on delays and to develop logical precedence orders of trains at certain operation points which can in turn be used in a sequential calculation of single train delay propagation. Furthermore, it endeavors to establish a basis to identify strongly connected groups of trains and stations, thus forming relevant subnets for further analysis

A Local Search Algorithm for Solving Large Scale Conflict Graphs in Freight Railway Timetabling

We consider the problem of planning the annual timetable for all freight trains in Germany simultaneously. That is, for each train, construct a slot through the network such that no two slots of different trains have a conflict. We denote this task by the Train Path Assignment Problem (TPAP) and consider a column generation approach where iteratively, we are given for each train request a growing set of possible slots. In each iteration, we look for a maximum subset without any conflicts. We model this problem as the Maximum Independent Set problem (MIS). Due to the many slots that are constructed, hence variables that are generated, we deal with large scale MIS instances. Therefore, we solve the MIS heuristically and develop a local search algorithm called Conflict Resolving (CR) that is tailored to the specially structured instances from the application. To solve the MIS, CR iteratively perturbs the current solution in order to leave local optima and then repeatedly improves the solution by replacing k-1 solution vertices by k non-solution vertices. These steps are embedded in a simulated annealing framework. In this paper, we present the column generation approach that is solved as an MIS. Furthermore, we introduce the CR algorithm and numerically compare it to both, a MIP solver and Iterated Local Search (ILS), a state-of-the-art heuristics. It turns out that CR performs best for the instances from real-world timetabling, and is also comparable to the ILS on selected MIS benchmark instances

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

A History of Universalism: Conceptions of the Internationality of Science from the Enlightenment to the Cold War

That science is fundamentally universal has been proclaimed innumerable times. But the precise geographical meaning of this universality has changed historically. This article examines conceptions of scientific internationalism from the Enlightenment to the Cold War, and their varying relations to cosmopolitanism, nationalism, socialism, and 'the West'. These views are confronted with recent tendencies to cast science as a uniquely European product

Suicide tourism: a pilot study on the Swiss phenomenon

While assisted suicide (AS) is strictly restricted in many countries, it is not clearly regulated by law in Switzerland. This imbalance leads to an influx of people—‘suicide tourists’—coming to Switzerland, mainly to the Canton of Zurich, for the sole purpose of committing suicide. Political debate regarding ‘suicide tourism’ is taking place in many countries. Swiss medicolegal experts are confronted with these cases almost daily, which prompted our scientific investigation of the phenomenon. The present study has three aims: (1) to determine selected details about AS in the study group (age, gender and country of residence of the suicide tourists, the organisation involved, the ingested substance leading to death and any diseases that were the main reason for AS); (2) to find out the countries from which suicide tourists come and to review existing laws in the top three in order to test the hypothesis that suicide tourism leads to the amendment of existing regulations in foreign countries; and (3) to compare our results with those of earlier studies in Zurich. We did a retrospective data analysis of the Zurich Institute of Legal Medicine database on AS of non-Swiss residents in the last 5 years (2008–2012), and internet research for current legislation and political debate in the three foreign countries most concerned. We analysed 611 cases from 31 countries all over the world. Non-terminal conditions such as neurological and rheumatic diseases are increasing among suicide tourists. The unique phenomenon of suicide tourism in Switzerland may indeed result in the amendment or supplementary guidelines to existing regulations in foreign countries