arXiv subjects

Jochen Lohmiller

Publications and source records attributed to Jochen Lohmiller.

5 recordsLinked to original sources

arXiv2021

Corridor for new mobility Aachen-Düsseldorf: Methods and concepts of the research project ACCorD

With the Corridor for New Mobility Aachen - Düsseldorf, an integrated development environment is created, incorporating existing test capabilities, to systematically test and validate automated vehicles in interaction with connected Intelligent Transport Systems Stations (ITS-Ss). This is achieved through a time- and cost-efficient toolchain and methodology, in which simulation, closed test sites as well as test fields in public transport are linked in the best possible way. By implementing a digital twin, the recorded traffic events can be visualized in real-time and driving functions can be tested in the simulation based on real data. In order to represent diverse traffic scenarios, the corridor contains a highway section, a rural area, and urban areas. First, this paper outlines the project goals before describing the individual project contents in more detail. These include the concepts of traffic detection, driving function development, digital twin development, and public involvement.

cs.CY↗

arXiv2017

Some Indications on how to Calibrate the Social Force Model of Pedestrian Dynamics

The Social Force Model of pedestrian dynamics is formulated in a way that a) most of its parameters do not have an immediate interpretation, b) often one single parameter has an impact on many aspects of walking behavior and c) a certain aspect of walking behavior results from the values of more than one parameter. This makes calibration difficult. The aim of this paper is to give practitioners an indication of how to proceed in the calibration process. For this by analytical transformations the parameters of the Social Force Model are related to real properties that have a clear and immediate meaning and which are also highly relevant result properties of a simulation: extent and clearance time of a queue, respectively maximum density and capacity flow. The theory for this is presented as well. As a side effect it can give a deeper understanding of the model for everyone interested in theoretical aspects.

physics.soc-ph↗

arXiv2017

Anatomizing deformation mechanisms in nanocrystalline Pd$_{90}$Au$_{10}$

We utilized synchrotron-based in-situ diffraction and dominant shear deformation to identify, dissect, and quantify the relevant deformation mechanisms in nanocrystalline $\mathrm{Pd}_{90}\mathrm{Au}_{10}$ in the limiting case of grain sizes at or below 10 nm. We could identify lattice and grain boundary elasticity, shear shuffling operating in the core region of grain boundaries, stress driven grain boundary migration, and dislocation shear along lattice planes to contribute, however, with significantly different and nontrivial stress-dependent shares to overall deformation. Regarding lattice elasticity, we find that Hookean linear elasticity prevailed up to the maximal stress value of $\approx$ 1.6 GPa. Shear shuffling that propagates strain at/along grain boundaries increases progressively with increasing load to carry about two thirds of the overall strain in the regime of macroplasticity. Stress driven grain boundary migration requires overcoming a threshold stress slightly below the yield stress of $\approx$ 1.4 GPa and contributes a share of $\approx$ 10% to overall strain. Appreciable dislocation activity begins at a stress value of $\approx$ 0.9 GPa to then increase and eventually propagate a maximal share of $\approx$ 15% to overall strain. In the stress regime below 0.9 GPa, which is characterized by a markedly decreasing tangent modulus, shear shuffling and lattice- and grain boundary elasticity operate exclusively. The material response in this regime seems indicative of nonlinear viscous behavior rather than being correlated with work- or strain hardening as observed in conventional fcc metals.

cond-mat.mtrl-sci↗

arXiv2015

The Social Force Model and its Relation to the Kladek Formula

It was recently found that the Social Force Model of pedestrian dynamics in a macroscopic limit for 1d movement does not reproduce the empirically found inflection point of the speed-density relation. It could be shown that, however, a simple and intuitively comprehensible extension of the Social Force Model shows the inflection point. Motivated by this observation in this contribution the relation of the Social Force Model with the Kladek formula for the speed-density relation of urban motorized traffic is discussed. Furthermore the models are compared to results data from experiments on vehicular, cycling, and pedestrian dynamics.

physics.soc-ph↗

arXiv2015

The Inflection Point of the Speed-Density Relation and the Social Force Model

It has been argued that the speed-density digram of pedestrian movement has an inflection point. This inflection point was found empirically in investigations of closed-loop single-file pedestrian movement. The reduced complexity of single-file movement does not only allow a higher precision for the evaluation of empirical data, but it occasionally also allows analytical considerations for micosimulation models. In this way it will be shown that certain (common) variants of the Social Force Model (SFM) do not produce an inflection point in the speed-density diagram if infinitely many pedestrians contribute to the force computed for one pedestrian. We propose a modified Social Force Model that produces the inflection point.

physics.soc-ph↗