
Billiard time machine
Dolanský, Jindřich ; Langer, Jiří (advisor) ; Novotný, Jan (referee) ; Hledík, Stanislav (referee)
Title: Billiard time machine Author: Jindřich Dolanský Department: Institute of Theoretical Physics Supervisor: doc. RNDr. Jiří Langer, CSc. Supervisor's email address: Jiri.Langer@mff.cuni.cz Abstract: In this work we investigate a simple interacting system of an elastic particle in the nonrelativistic spacetime with a nontrivial causal structure realized by a worm hole with a time shift. We require that standard local physical laws hold, and search for their globally consistent solutions, i.e, we assume the validity of the principle of selfconsistency. If there were nontrivial set of initial conditions which would violate this principle, the system would be logically inconsistent. We show that the investigated system is not inconsistent in this sense, i.e., that all standard initial conditions have a globally consistent evolution. Even for the so called dangerous initial conditions which threaten to result into the paradoxical situation a consistent solution exists. In this case, the paradoxical collisionfree trajectory is superseded by a special consistent selfcolliding trajectory. Moreover, we demonstrate that more than one globally consistent evolution exists for a wide class of initial conditions. Thus, the evolution of the described system is not unique due to the nontrivial causal structure...


Billiard time machine
Dolanský, Jindřich ; Langer, Jiří (advisor) ; Novotný, Jan (referee) ; Hledík, Stanislav (referee)
Title: Billiard time machine Author: Jindřich Dolanský Department: Institute of Theoretical Physics Supervisor: doc. RNDr. Jiří Langer, CSc. Supervisor's email address: Jiri.Langer@mff.cuni.cz Abstract: In this work we investigate a simple interacting system of an elastic particle in the nonrelativistic spacetime with a nontrivial causal structure realized by a worm hole with a time shift. We require that standard local physical laws hold, and search for their globally consistent solutions, i.e, we assume the validity of the principle of selfconsistency. If there were nontrivial set of initial conditions which would violate this principle, the system would be logically inconsistent. We show that the investigated system is not inconsistent in this sense, i.e., that all standard initial conditions have a globally consistent evolution. Even for the so called dangerous initial conditions which threaten to result into the paradoxical situation a consistent solution exists. In this case, the paradoxical collisionfree trajectory is superseded by a special consistent selfcolliding trajectory. Moreover, we demonstrate that more than one globally consistent evolution exists for a wide class of initial conditions. Thus, the evolution of the described system is not unique due to the nontrivial causal structure...


Simulation of particle motion in a closed conduit validated against experimental data
Dolanský, Jindřich
Motion of a number of spherical particles in a closed conduit is examined by means of both simulation and experiment. The bed of the conduit is covered by stationary spherical particles of the size of the moving particles. The flow is driven by experimentally measured velocity profiles which are inputs of the simulation. Altering input velocity profiles generates various trajectory patterns. The lattice Boltzmann method (LBM) based simulation is developed to study mutual interactions of the flow and the particles. The simulation enables to model both the particle motion and the fluid flow. The entropic LBM is employed to deal with the flow characterized by the high Reynolds number. The entropic modification of the LBM along with the enhanced refinement of the lattice grid yield an increase in demands on computational resources. Due to the inherently parallel nature of the LBM it can be handled by employing the Parallel Computing Toolbox (MATLAB) and other transformations enabling usage of the CUDA GPU computing technology. The trajectories of the particles determined within the LBM simulation are validated against data gained from the experiments. The compatibility of the simulation results with the outputs of experimental measurements is evaluated. The accuracy of the applied approach is assessed and stability and efficiency of the simulation is also considered.


Simulation of motion of multiple particles in a closed conduit using the LBM based approach
Dolanský, Jindřich
The twodimensional numerical model of motion of multiple circular particles in fluid flow based on the lattice Boltzmann method (LBM) is presented. The flow is driven by the powerlaw velocity profile at the inlet in a closed horizontal conduit. Motion of particles consists of free motion in the flow, particlebed and particleparticle collisions. The simulation for both movements of particles and velocity field of the flow is developed. Stability issues of the simulation are considered and a resolution using the entropic LBM and extension of computational resources is proposed. Finally, an enhancement of the simulation for more complex processes is suggested


Simulation of saltation motion using LBE based methods
Dolanský, Jindřich
The numerical model of the motion of the circular particle close to the bed in an open channel with a rugged bed based on the lattice Boltzmann method (LBM) is presented. The LBM is used as a DNS approach in which hydrodynamic forces are expressed as sum of contributions from fluid elements interacting with the moving particle. The corresponding numerical simulation for the saltation motion which represents a dominant mode of the bed load transport is developed. Flow is driven by the logarithmic velocity profile at the inlet of a two dimensional channel with a bed formed by semicircles of variable radii in a bed of particles. Translational and rotational movements of the particle are induced by gravitational force on one hand, and by hydrodynamic forces on the other hand. The LBE (lattice Boltzmann equation) based simulation provides the opportunity to study the behavior of saltation motion in the moderate and high Reynolds number regimes. Most of the input parameters, including boundary conditions or flow conditions, are adjustable within a range of values. Stability issues of the simulation are considered and a resolution using a combination of different LBE models and the extension of computational resources is proposed. Finally, an enhancement of the simulation for more complex processes is suggested.


Grey Literature Repositories
Pejšová, Petra ; Vaska, Marcus ; Schöpfel, Joachim ; Fürstová, Iveta ; Polčák, Radim ; Mach, Jan ; Frantíková, Bohdana ; Karlach, Petr ; Dolanský, Jindřich ; Svoboda, Martin
The book Grey Literature Repositories provides information about the concept of grey literature, its development, types, and producers in the European context, with a focus on the Czech Republic. The example of the National Repository of Grey Literature, practically implemented in the National Technical Library, is given to illustrate how such a repository may be built. The most important factors in the success of such project are cooperation and legislation. The book presents the components necessary to construct a repository from a practical viewpoint, namely analysis, selection and implementation of software, creation of the metadata format and audit of repository credibility.
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