Combinatorial optimization model for railway engine assignment problem

This paper presents an experimental study for the Hungarian State Railway Company (M\'AV). The engine assignment problem was solved at M\'AV by their experts without using any explicit operations research tool. Furthermore, the operations research model was not known at the company. The goal of our project was to introduce and solve an operations research model for the engine assignment problem on real data sets. For the engine assignment problem we are using a combinatorial optimization model. At this stage of research the single type train that is pulled by a single type engine is modeled and solved for real data. There are two regions in Hungary where the methodology described in this paper can be used and M\'AV started to use it regularly. There is a need to generalize the model for multiple type trains and multiple type engines

Solving order constraints in logarithmic space.

We combine methods of order theory, finite model theory, and universal algebra to study, within the constraint satisfaction framework, the complexity of some well-known combinatorial problems connected with a finite poset. We identify some conditions on a poset which guarantee solvability of the problems in (deterministic, symmetric, or non-deterministic) logarithmic space. On the example of order constraints we study how a certain algebraic invariance property is related to solvability of a constraint satisfaction problem in non-deterministic logarithmic space

Fully Dynamic Maintenance of Arc-Flags in Road Networks

International audienceThe problem of finding best routes in road networks can be solved by applying Dijkstra's shortest paths algorithm. Unfortunately, road networks deriving from real-world applications are huge yielding unsustainable times to compute shortest paths. For this reason, great research efforts have been done to accelerate Dijkstra's algorithm on road networks. These efforts have led to the development of a number of speed-up techniques, as for example Arc-Flags, whose aim is to compute additional data in a preprocessing phase in order to accelerate the shortest paths queries in an on-line phase. The main drawback of most of these techniques is that they do not work well in dynamic scenarios. In this paper we propose a new algorithm to update the Arc-Flags of a graph subject to edge weight decrease operations. To check the practical performances of the new algorithm we experimentally analyze it, along with a previously known algorithm for edge weight increase operations, on real-world road networks subject to fully dynamic sequences of operations. Our experiments show a significant speed-up in the updating phase of the Arc-Flags, at the cost of a small space and time overhead in the preprocessing phase

Molecular dynamics approach: from chaotic to statistical properties of compound nuclei

Statistical aspects of the dynamics of chaotic scattering in the classical model of $\alpha$-cluster nuclei are studied. It is found that the dynamics governed by hyperbolic instabilities which results in an exponential decay of the survival probability evolves to a limiting energy distribution whose density develops the Boltzmann form. The angular distribution of the corresponding decay products shows symmetry with respect to $\pi/2$ angle. Time estimated for the compound nucleus formation ranges within the order of $10^{-21}$s.Comment: 11 pages, LaTeX, non

The Mannheim Corona study: life in Germany in a state of emergency : report for March 20 to May 28, 2020, English translation of the original report (in German)

We are all affected by the corona pandemic and the measures taken by the federal government to decelerate the spread of the virus. At the University of Mannheim, we have developed a survey instrument over the past eight years which we can use to quickly examine the social implications of the pandemic in Germany. To the best of our knowledge, our study is the only one in Germany which can assess how the corona crisis is affecting people’s lives in Germany on a daily basis. That is why we consider it as our social duty to contribute to a better understanding of how the corona crisis is affecting the population and to inform the public as well as decision-makers in politics and business about current developments. The Mannheim Corona Study started on Friday, March 20. The study is carried out daily and reports on life in Germany during the corona crisis. We examine social and economic aspects (such as childcare, employment situations, and disposable income), the influence of political measures on social interactions, anxiety as well as public acceptance of the measures taken to contain the pan

The level set method for the two-sided eigenproblem

We consider the max-plus analogue of the eigenproblem for matrix pencils Ax=lambda Bx. We show that the spectrum of (A,B) (i.e., the set of possible values of lambda), which is a finite union of intervals, can be computed in pseudo-polynomial number of operations, by a (pseudo-polynomial) number of calls to an oracle that computes the value of a mean payoff game. The proof relies on the introduction of a spectral function, which we interpret in terms of the least Chebyshev distance between Ax and lambda Bx. The spectrum is obtained as the zero level set of this function.Comment: 34 pages, 4 figures. Changes with respect to the previous version: we explain relation to mean-payoff games and discrete event systems, and show that the reconstruction of spectrum is pseudopolynomia

The Mannheim Corona Study: Life in Germany in a state of emergency : Report for March 20 to June 30, 2020 ; English translation of the original report (in German)

We are all affected by the corona pandemic and the measures taken by the federal government to decelerate the spread of the virus. At the University of Mannheim, we have developed a survey instrument over the past eight years which we can use to quickly examine the social implications of the pandemic in Germany. To the best of our knowledge, our study is the only one in Germany which can assess how the corona crisis is affecting people’s lives in Germany on a daily basis. That is why we consider it as our social duty to contribute to a better understanding of how the corona crisis is affecting the population and to inform the public as well as decision-makers in politics and business about current developments

The Mannheim Corona study: Life in Germany in a state of emergency : Report for March 20 to July 09, 2020

We are all affected by the corona pandemic and the measures taken by the federal government to decelerate the spread of the virus. At the University of Mannheim, we have developed a survey instrument over the past eight years which we can use to quickly examine the social implications of the pandemic in Germany. To the best of our knowledge, our study is the only one in Germany which can assess how the corona crisis is affecting people’s lives in Germany on a daily basis. That is why we consider it as our social duty to contribute to a better understanding of how the corona crisis is affecting the population and to inform the public as well as decision-makers in politics and business about current developments. The Mannheim Corona Study started on Friday, March 20. The study is carried out daily and reports on life in Germany during the corona crisis. We examine social and economic aspects (such as childcare, employment situations, and disposable income), the influence of political measures on social interactions, anxiety as well as public acceptance of the measures taken to contain the pandemic. Between 411 und 643 (on average 489) respondents take part in the study every day

Terrestrial Implications of Cosmological Gamma-Ray Burst Models

The observation by the BATSE instrument on the Compton Gamma Ray Observatory that gamma-ray bursts (GRBs) are distributed isotropically around the Earth but nonuniformly in distance has led to the widespread conclusion that GRBs are most likely to be at cosmological distances, making them the most luminous sources known in the Universe. If bursts arise from events that occur in normal galaxies, such as neutron star binary inspirals, then they will also occur in our Galaxy about every hundred thousand to million years. The gamma-ray flux at the Earth due to a Galactic GRB would far exceed that from even the largest solar flares. The absorption of this radiation in the atmosphere would substantially increase the stratospheric nitric oxide concentration through photodissociation of N$_2$, greatly reducing the ozone concentration for several years through NO$_x$ catalysis, with important biospheric effects due to increased solar ultraviolet flux. A nearby GRB may also leave traces in anomalous radionuclide abundances.Comment: uuencoded, gzip-ed postscript; 6 pages; submitted to ApJ Letter