Günter Radons - Academia.edu (original) (raw)

Papers by Günter Radons

International journal of radiation biology and related studies in physics, chemistry, and medicine

X-irradiation of single crystals of uridine-5'-phosphate (disodium salt) between 10 and 3... more X-irradiation of single crystals of uridine-5'-phosphate (disodium salt) between 10 and 300 K as well as storage of irradiated crystals at 300 K produces at least seven different radical species. Between 10 and 77 K, the uracil base anion and a secondary alkoxy radical at the ribose-O3'-site are formed. The latter transforms into a C5'-centred alkylphosphate species between 110 and 130 K which in turn decays between 180 and 220 K under formation of a base 5-yl hydrogen addition radical. Irradiation at 300 K additionally produces the base-located 6-yl radical together with a radical tentatively assigned to the doubly protonated base anion. Storage of crystals for several months results in decay of most of these species leaving a radical possibly located at c5' of the ribose. The spectral parameters of these radicals are given and discussed.

Summary. We show that the coupling of simple dynamical systems with a typical model for hysteresi... more Summary. We show that the coupling of simple dynamical systems with a typical model for hysteresis, the Preisach model, leads to interesting new scenarios in non-linear dynamics. The Preisach model is known from many branches of science to be a universal model for ...

IEEE Signal Processing Letters

ABSTRACT

IFAC-PapersOnLine, 2015

The identification of the stability lobes for machine-tool vibrations is presented for interrupte... more The identification of the stability lobes for machine-tool vibrations is presented for interrupted turning processes with round inserts. An analytic cutting force model for round inserts is derived, where the directional factors depend nonlinear and non-homogeneous on the depth of cut. Furthermore, the effect of vibrations in the cutting speed direction on the chip thickness modulation is taken into account, which leads to a state-dependent delay. A multifrequency solution is presented for the stability analysis of metal cutting processes, where the cutting force is characterized by periodic coefficients and state-dependent delays.

Hydrodynamic Lyapunov modes, which have recently been observed in many extended systems with tran... more Hydrodynamic Lyapunov modes, which have recently been observed in many extended systems with translational symmetry, such as hard sphere systems, dynamic XY-models, or Lennard-Jones fluids, are nowadays regarded as fundamental objects connecting Nonlinear Dynamics and Statistical Physics. A solution to one of the puzzles, the appearance of good and of ``vague'' modes, is presented here for the model system of coupled map lattices: The structural properties of these modes are related to the phase space geometry, especially the angles between Oseledec subspaces, and to fluctuations of local Lyapunov exponents. The numerical calculation of these quantities is achieved with the new algorithm proposed in [1]. In this context we report also on the possible appearance of branches in the Lyapunov spectra of inhomogeneous systems [2], similar to acoustic and optical branches for phonons. [1] F. Ginelli et al., PRL 99, 130601 (2007) [2] H. Yang and G. Radons, PRL 99, 164101 (2007)

A frequently encountered situation in the study of delay systems is that the length of the delay ... more A frequently encountered situation in the study of delay systems is that the length of the delay time changes with time, which is of relevance in many fields such as optics, mechanical machining, biology or physiology. A characteristic feature of such systems is that the dimension of the system dynamics collapses due to the fluctuations of delay times. In consequence, the support of the long-trajectory attractors of this kind of systems is found being fractal in contrast to the fuzzy attractors in most random systems.

In single molecule experiments dye molecules are used to trace dynamics e.g. of diffusing DNA alo... more In single molecule experiments dye molecules are used to trace dynamics e.g. of diffusing DNA along membranes. We used Rhodamine B as a probe to study the microscopic mobility in an organic liquid (TEHOS) at the interface with a solid (Si wafer with 100 nm thermally grown SiO 2 ) via video wide-field microscopy. In previous experiments [1] we were able to show that diffusion within ultrathin liquid films is heterogeneous and drastically slowed down in comparison to bulk behaviour. Recent time series of 2 -10 nm thin films revealed the influence of surface changes and of film thinning on the molecular mobility within such ultrathin films. It is well known that liquids show layering at interfaces with solids [2], therefore dynamic inhomogeneities in diffusion, caused by different dye mobility within different layers and by layer interchange of dye molecules during the observation, might explain the observed heterogeneities. Recent reports [3] as well as our own observations indicate additional static inhomogeneities caused by surface heterogeneities.

Lecture Notes in Computer Science, 2006

... A system of 2dN × 2dN linear and 2dN nonlinear ordinary differential equations has to be inte... more ... A system of 2dN × 2dN linear and 2dN nonlinear ordinary differential equations has to be integrated simulta-neously in order to obtain the dynamics of 2dN ... addition an optimal balancing of computation and communication on distributed memory machines or cluster of SMPs. ...

An der TU Chemnitz haben sich seit über zwei Jahrzehnten die Gebiete der rechnergestützten Wissen... more An der TU Chemnitz haben sich seit über zwei Jahrzehnten die Gebiete der rechnergestützten Wissenschaften (Computational Science) sowie des parallelen und verteilten Hochleistungsrechnens mit zunehmender Verzahnung entwickelt. Die Koordinierung und Bündelung entsprechender Forschungsarbeiten in der Profillinie 6 “Modellierung, Simulation, Hochleistungsrechnen” wird es ermöglichen, im internationalen Wettbewerb des Wissens mitzuhalten.

Lecture Notes in Computational Science and Engineering, 2006

ABSTRACT

Physical Review E, 1996

ABSTRACT

Physical Review Letters, 2014

Momentum diffusion is a widespread phenomenon in generic Hamiltonian systems. We show for the pro... more Momentum diffusion is a widespread phenomenon in generic Hamiltonian systems. We show for the prototypical standard map that this implies weak ergodicity breaking for the superdiffusive transport in coordinate direction with an averaging-dependent quadratic and cubic increase of the mean-squared displacement (MSD), respectively. This is explained via integrated Brownian motion, for which we derive aging time dependent expressions for the ensemble-averaged MSD, the distribution of time-averaged MSDs, and the ergodicity breaking parameter. Generalizations to other systems showing momentum diffusion are pointed out.

Physical Review E, 2014

Stripe patterns, observed in a large variety of physical systems, often exhibit a slow nonequilib... more Stripe patterns, observed in a large variety of physical systems, often exhibit a slow nonequilibrium dynamics because ordering is impeded by the presence of topological defects. Using computer simulations based on a well-established model for stripe formation, we show that a slow dynamics and aging occur also in stripe patterns free of topological defects. For a wide range of noise strengths, the two-time orientation correlation function follows a scaling form that is typical for systems exhibiting a growing length scale. In our case, the underlying mechanism is the coarsening of orientation fluctuations, ultimately leading to power-law spatial correlations perpendicular to the stripes. Our results show that even for the smallest amount of noise, stripe phases without topological defects do not reach equilibrium. This constitutes an important aspect of the dynamics of modulated phases.

Physica D: Nonlinear Phenomena, 2004

... transport properties such as the total suppression of chaotic diffusion and anomalous drift. ... more ... transport properties such as the total suppression of chaotic diffusion and anomalous drift. The relation to random walks in random environments, in particular to the Sinai model, explains also the occurrence of ageing in such dynamical systems. Anomalous transport is ...

Physical Review Letters, 2006

Numerical and analytical evidence is presented to show that hydrodynamic Lyapunov modes (HLMs) do... more Numerical and analytical evidence is presented to show that hydrodynamic Lyapunov modes (HLMs) do exist in lattices of coupled Hamiltonian and dissipative maps. More importantly, we find that HLMs in these two classes of systems are different with respect to their spatial structure and their dynamical behavior. To be concrete, the corresponding dispersion relations of Lyapunov exponent versus wave number are characterized by lambda approximately k and lambda approximately k2, respectively. The HLMs in Hamiltonian systems are propagating, whereas those of dissipative systems show only diffusive motion. Extensive numerical simulations of various systems confirm that the existence of HLMs is a very general feature of extended dynamical systems with continuous symmetries and that the above-mentioned differences between the two classes of systems are universal in large extent.

Physical Review E, 2000

In our recent paper [Phys. Rev. E 58, 1789 (1998)] we found notable deviations from a power-law d... more In our recent paper [Phys. Rev. E 58, 1789 (1998)] we found notable deviations from a power-law decay for the "magnetization" of a system of coupled phase oscillators with random interactions claimed by Daido in Phys. Rev. Lett. 68, 1072 (1992). For another long-time property, the Lyaponov exponent, we found that his numerical procedure showed strong time discretization effects and we suspected a similar effect for the algebraic decay. In the Comment to our paper [preceding paper, Phys. Rev. E 61, 2145 (2000)] Daido made clear that the power law behavior was only claimed for the sample averaged magnetization [Z] and he presented new, more accurate numerical results which provide evidence for a power-law decay of this quantity. Our results, however, were obtained for Z itself and not for [Z]. In addition, we have taken the intrinsic oscillator frequencies as Gaussian random variables, while Daido in his new and apparently also in his earlier simulations used a deterministic approximation to the Gaussian distribution. Due to the differences in the observed quantity and the model assumptions our and Daido's results may be compatible.

International journal of radiation biology and related studies in physics, chemistry, and medicine

X-irradiation of single crystals of uridine-5'-phosphate (disodium salt) between 10 and 3... more X-irradiation of single crystals of uridine-5'-phosphate (disodium salt) between 10 and 300 K as well as storage of irradiated crystals at 300 K produces at least seven different radical species. Between 10 and 77 K, the uracil base anion and a secondary alkoxy radical at the ribose-O3'-site are formed. The latter transforms into a C5'-centred alkylphosphate species between 110 and 130 K which in turn decays between 180 and 220 K under formation of a base 5-yl hydrogen addition radical. Irradiation at 300 K additionally produces the base-located 6-yl radical together with a radical tentatively assigned to the doubly protonated base anion. Storage of crystals for several months results in decay of most of these species leaving a radical possibly located at c5' of the ribose. The spectral parameters of these radicals are given and discussed.

Summary. We show that the coupling of simple dynamical systems with a typical model for hysteresi... more Summary. We show that the coupling of simple dynamical systems with a typical model for hysteresis, the Preisach model, leads to interesting new scenarios in non-linear dynamics. The Preisach model is known from many branches of science to be a universal model for ...

IEEE Signal Processing Letters

ABSTRACT

IFAC-PapersOnLine, 2015

The identification of the stability lobes for machine-tool vibrations is presented for interrupte... more The identification of the stability lobes for machine-tool vibrations is presented for interrupted turning processes with round inserts. An analytic cutting force model for round inserts is derived, where the directional factors depend nonlinear and non-homogeneous on the depth of cut. Furthermore, the effect of vibrations in the cutting speed direction on the chip thickness modulation is taken into account, which leads to a state-dependent delay. A multifrequency solution is presented for the stability analysis of metal cutting processes, where the cutting force is characterized by periodic coefficients and state-dependent delays.

Hydrodynamic Lyapunov modes, which have recently been observed in many extended systems with tran... more Hydrodynamic Lyapunov modes, which have recently been observed in many extended systems with translational symmetry, such as hard sphere systems, dynamic XY-models, or Lennard-Jones fluids, are nowadays regarded as fundamental objects connecting Nonlinear Dynamics and Statistical Physics. A solution to one of the puzzles, the appearance of good and of ``vague'' modes, is presented here for the model system of coupled map lattices: The structural properties of these modes are related to the phase space geometry, especially the angles between Oseledec subspaces, and to fluctuations of local Lyapunov exponents. The numerical calculation of these quantities is achieved with the new algorithm proposed in [1]. In this context we report also on the possible appearance of branches in the Lyapunov spectra of inhomogeneous systems [2], similar to acoustic and optical branches for phonons. [1] F. Ginelli et al., PRL 99, 130601 (2007) [2] H. Yang and G. Radons, PRL 99, 164101 (2007)

A frequently encountered situation in the study of delay systems is that the length of the delay ... more A frequently encountered situation in the study of delay systems is that the length of the delay time changes with time, which is of relevance in many fields such as optics, mechanical machining, biology or physiology. A characteristic feature of such systems is that the dimension of the system dynamics collapses due to the fluctuations of delay times. In consequence, the support of the long-trajectory attractors of this kind of systems is found being fractal in contrast to the fuzzy attractors in most random systems.

In single molecule experiments dye molecules are used to trace dynamics e.g. of diffusing DNA alo... more In single molecule experiments dye molecules are used to trace dynamics e.g. of diffusing DNA along membranes. We used Rhodamine B as a probe to study the microscopic mobility in an organic liquid (TEHOS) at the interface with a solid (Si wafer with 100 nm thermally grown SiO 2 ) via video wide-field microscopy. In previous experiments [1] we were able to show that diffusion within ultrathin liquid films is heterogeneous and drastically slowed down in comparison to bulk behaviour. Recent time series of 2 -10 nm thin films revealed the influence of surface changes and of film thinning on the molecular mobility within such ultrathin films. It is well known that liquids show layering at interfaces with solids [2], therefore dynamic inhomogeneities in diffusion, caused by different dye mobility within different layers and by layer interchange of dye molecules during the observation, might explain the observed heterogeneities. Recent reports [3] as well as our own observations indicate additional static inhomogeneities caused by surface heterogeneities.

Lecture Notes in Computer Science, 2006

... A system of 2dN × 2dN linear and 2dN nonlinear ordinary differential equations has to be inte... more ... A system of 2dN × 2dN linear and 2dN nonlinear ordinary differential equations has to be integrated simulta-neously in order to obtain the dynamics of 2dN ... addition an optimal balancing of computation and communication on distributed memory machines or cluster of SMPs. ...

An der TU Chemnitz haben sich seit über zwei Jahrzehnten die Gebiete der rechnergestützten Wissen... more An der TU Chemnitz haben sich seit über zwei Jahrzehnten die Gebiete der rechnergestützten Wissenschaften (Computational Science) sowie des parallelen und verteilten Hochleistungsrechnens mit zunehmender Verzahnung entwickelt. Die Koordinierung und Bündelung entsprechender Forschungsarbeiten in der Profillinie 6 “Modellierung, Simulation, Hochleistungsrechnen” wird es ermöglichen, im internationalen Wettbewerb des Wissens mitzuhalten.

Lecture Notes in Computational Science and Engineering, 2006

ABSTRACT

Physical Review E, 1996

ABSTRACT

Physical Review Letters, 2014

Momentum diffusion is a widespread phenomenon in generic Hamiltonian systems. We show for the pro... more Momentum diffusion is a widespread phenomenon in generic Hamiltonian systems. We show for the prototypical standard map that this implies weak ergodicity breaking for the superdiffusive transport in coordinate direction with an averaging-dependent quadratic and cubic increase of the mean-squared displacement (MSD), respectively. This is explained via integrated Brownian motion, for which we derive aging time dependent expressions for the ensemble-averaged MSD, the distribution of time-averaged MSDs, and the ergodicity breaking parameter. Generalizations to other systems showing momentum diffusion are pointed out.

Physical Review E, 2014

Stripe patterns, observed in a large variety of physical systems, often exhibit a slow nonequilib... more Stripe patterns, observed in a large variety of physical systems, often exhibit a slow nonequilibrium dynamics because ordering is impeded by the presence of topological defects. Using computer simulations based on a well-established model for stripe formation, we show that a slow dynamics and aging occur also in stripe patterns free of topological defects. For a wide range of noise strengths, the two-time orientation correlation function follows a scaling form that is typical for systems exhibiting a growing length scale. In our case, the underlying mechanism is the coarsening of orientation fluctuations, ultimately leading to power-law spatial correlations perpendicular to the stripes. Our results show that even for the smallest amount of noise, stripe phases without topological defects do not reach equilibrium. This constitutes an important aspect of the dynamics of modulated phases.

Physica D: Nonlinear Phenomena, 2004

... transport properties such as the total suppression of chaotic diffusion and anomalous drift. ... more ... transport properties such as the total suppression of chaotic diffusion and anomalous drift. The relation to random walks in random environments, in particular to the Sinai model, explains also the occurrence of ageing in such dynamical systems. Anomalous transport is ...

Physical Review Letters, 2006

Numerical and analytical evidence is presented to show that hydrodynamic Lyapunov modes (HLMs) do... more Numerical and analytical evidence is presented to show that hydrodynamic Lyapunov modes (HLMs) do exist in lattices of coupled Hamiltonian and dissipative maps. More importantly, we find that HLMs in these two classes of systems are different with respect to their spatial structure and their dynamical behavior. To be concrete, the corresponding dispersion relations of Lyapunov exponent versus wave number are characterized by lambda approximately k and lambda approximately k2, respectively. The HLMs in Hamiltonian systems are propagating, whereas those of dissipative systems show only diffusive motion. Extensive numerical simulations of various systems confirm that the existence of HLMs is a very general feature of extended dynamical systems with continuous symmetries and that the above-mentioned differences between the two classes of systems are universal in large extent.

Physical Review E, 2000

In our recent paper [Phys. Rev. E 58, 1789 (1998)] we found notable deviations from a power-law d... more In our recent paper [Phys. Rev. E 58, 1789 (1998)] we found notable deviations from a power-law decay for the "magnetization" of a system of coupled phase oscillators with random interactions claimed by Daido in Phys. Rev. Lett. 68, 1072 (1992). For another long-time property, the Lyaponov exponent, we found that his numerical procedure showed strong time discretization effects and we suspected a similar effect for the algebraic decay. In the Comment to our paper [preceding paper, Phys. Rev. E 61, 2145 (2000)] Daido made clear that the power law behavior was only claimed for the sample averaged magnetization [Z] and he presented new, more accurate numerical results which provide evidence for a power-law decay of this quantity. Our results, however, were obtained for Z itself and not for [Z]. In addition, we have taken the intrinsic oscillator frequencies as Gaussian random variables, while Daido in his new and apparently also in his earlier simulations used a deterministic approximation to the Gaussian distribution. Due to the differences in the observed quantity and the model assumptions our and Daido's results may be compatible.