Martin Kröger

Last Name

Kröger

First Name

Martin

ORCID

0000-0003-1402-6714

Organisational unit

03986 - Gambardella, Pietro / Gambardella, Pietro

Show all metadata

Search Results

Publications 1 - 10 of 308

Molecular dynamics of model liquid crystals composed of semiflexible molecules
Affouard, F.; Kröger, Martin; Hess, S. (1996)
Physical Review E
Particle transport and finite-size effects in Lorentz channels with finite horizons
Cirillo, Emilio N.M.; Colangeli, Matteo; Kröger, Martin; et al. (2025)
Physica D: Nonlinear Phenomena
Particle transport is investigated in a finite-size realization of the classical Lorentz gas model. We consider point particles moving at constant speed in a 2D rectangular strip of finite length, filled with circular scatterers sitting at the vertices of a triangular lattice. Particles are injected at the left boundary with a prescribed rate, undergo specular reflections when colliding with the scatterers and the horizontal boundaries of the channel, and are finally absorbed at the left or the right boundary. Thanks to the equivalence with give Correlated Random Walks, in the finite horizon case, we show that the inverse probability that a particle exits through the right boundary depends linearly on the number of cells in the channel. A non-monotonic behavior of such probability as a function of the density of scatterers is also discussed and traced back analytically to the geometric features of a single trap. This way, we do not refer to asymptotic quantities and we accurately quantify the finite size effects. Our deterministic model provides a microscopic support for a variety of phenomenological laws, e.g. the Darcy’s law for porous media and the Ohm’s law in electronic transport.
Time is Length in Self-Similar Logarithmic Aging of Physically Cross-Linked Semiflexible Polymer Networks
Ilg, Patrick; Luap, Clarisse; Kröger, Martin (2025)
Physical Review Letters
Physical aging in polymers is a fundamental yet poorly understood phenomenon, as diverse macromolecular systems exhibit remarkably similar slow dynamics. Through molecular dynamics simulations of physically cross-linked networks composed of semiflexible polymers, we identify a previously unexplored class of self-similar aging. The network undergoes ultraslow coarsening charac terized by a logarithmically growing mesh size, LðtÞ ∼ ln t, which governs the spatial organization, cohesive and bending energies, and the aging dynamics of the system. This single time-dependent length scale defines an internal clock, giving rise to spatiotemporal self-similarity of both structure and dynamics —offering a perspective on aging in soft and disordered materials.
Polymer brushes under shear: Molecular dynamics simulations compared to experiments
Singh, Manjesh K.; Ilg, Patrick; Espinosa-Marzal, Rosa M.; et al. (2015)
Langmuir
On the Analytical Solution of the SIRV-Model for the Temporal Evolution of Epidemics for General Time-Dependent Recovery, Infection and Vaccination Rates
Kröger, Martin; Schlickeiser, Reinhard (2024)
Mathematics
The susceptible–infected–recovered/removed–vaccinated (SIRV) epidemic model is an important generalization of the SIR epidemic model, as it accounts quantitatively for the effects of vaccination campaigns on the temporal evolution of epidemic outbreaks. Additional to the time-dependent infection (a(t)) and recovery (µ(t)) rates, regulating the transitions between the compartments S → I and I → R, respectively, the time-dependent vaccination rate v(t) accounts for the transition between the compartments S → V of susceptible to vaccinated fractions. An accurate analytical approximation is derived for arbitrary and different temporal dependencies of the rates, which is valid for all times after the start of the epidemics for which the cumulative fraction of new infections J(t) ≪ 1. As vaccination campaigns automatically reduce the rate of new infections by transferring persons from susceptible to vaccinated, the limit J(t) ≪ 1 is even better fulfilled than in the SIR-epidemic model. The comparison of the analytical approximation for the temporal dependence of the rate of new infections ˚J(t) = a(t)S(t)I(t), the corresponding cumulative fraction J(t), and V(t), respectively, with the exact numerical solution of the SIRV-equations for different illustrative examples proves the accuracy of our approach. The considered illustrative examples include the cases of stationary ratios with a delayed start of vaccinations, and an oscillating ratio of recovery to infection rate with a delayed vaccination at constant rate. The proposed analytical approximation is self-regulating as the final analytical expression for the cumulative fraction J∞ after infinite time allows us to check the validity of the original assumption J(t) ≤ J∞ ≪ 1.
Miscibility and Nanoparticle Diffusion in Ionic Nanocomposites
Karatrantos, Argyrios, V; Koutsawa, Yao; Dubois, Philippe; et al. (2018)
Polymers
We investigate the effect of various spherical nanoparticles in a polymer matrix on dispersion, chain dimensions and entanglements for ionic nanocomposites at dilute and high nanoparticle loading by means of molecular dynamics simulations. The nanoparticle dispersion can be achieved in oligomer matrices due to the presence of electrostatic interactions. We show that the overall configuration of ionic oligomer chains, as characterized by their radii of gyration, can be perturbed at dilute nanoparticle loading by the presence of charged nanoparticles. In addition, the nanoparticle’s diffusivity is reduced due to the electrostatic interactions, in comparison to conventional nanocomposites where the electrostatic interaction is absent. The charged nanoparticles are found to move by a hopping mechanism.
Flow-alignment and rheology of polymer melts
Kröger, Martin (1994)
Macromolecular Symposia
Rheological Evidence for a Dynamical Crossover in Polymer Melts via Nonequilibrium Molecular Dynamics
Kröger, Martin; Hess, Siegfried (2000)
Physical Review Letters
Chaotic orientational behavior of a nematic liquid crystal subjected to a steady shear flow
Rienäcker, Götz; Kröger, Martin; Hess, Siegfried (2002)
Physical Review E
Publication specific impact of articles published by rheological journals
Kröger, Martin (2005)
Applied rheology

Publications 1 - 10 of 308

Martin Kröger

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results