DSpace Kolekce:http://hdl.handle.net/11025/348112024-03-28T22:12:04Z2024-03-28T22:12:04ZWang tiling for particle heterogeneous materials: algorithms for generation of tiles/cubes via molecular dynamicsŠedlbauer, DavidLepš, Matějhttp://hdl.handle.net/11025/348312021-09-22T08:43:21Z2019-01-01T00:00:00ZNázev: Wang tiling for particle heterogeneous materials: algorithms for generation of tiles/cubes via molecular dynamics
Autoři: Šedlbauer, David; Lepš, Matěj
Abstrakt: This paper aims at a reduction of periodicity artefacts during a generation of random heterogeneous material
models. The traditional concept of the Periodic Unit Cell is compared with a novel approach of the stochastic
Wang tiling. Since modelled structures consist of hard circular/spherical particles in a matrix, the algorithm for
placement of inclusions is based on themodifiedmolecular dynamics.We introduce two types ofWang tile boundary
conditions to decrease periodicity artefacts. Tested samples for 2D applications form sets of both monodisperse and
polydisperse microstructures. The overall volume fractions of these samples are approximately 0.2, 0.4, and 0.6,
respectively. The generated sets are analysed both visually and statistically via a two-point probability function.
An extension of the stochastic Wang tiling enables to create 3D structures, as well. Therefore, artificial periodicity
is also investigated on a 3D sample consisting of spherical particles of identical radii distributed in a continuous
phase.2019-01-01T00:00:00ZŠedlbauer, DavidLepš, MatějResponse probability density of a system with cross-correlated parametric and additive input noisesNáprstek, JiříFisher, Cyrilhttp://hdl.handle.net/11025/348302021-09-22T08:43:21Z2019-01-01T00:00:00ZNázev: Response probability density of a system with cross-correlated parametric and additive input noises
Autoři: Náprstek, Jiří; Fisher, Cyril
Abstrakt: Data processing and subsequent mining is a widely followed task. Employment of suitable evaluation and in-
terpretation procedures can significantly improve the effective resolution of measuring facility using an identical
hardware equipment. Recording of time variable processes is accompanied by various internal disturbing effects
as a rule. They influence parameters of the measuring facility, transducer-device transmitting, etc. These parasitic
processes are usually of the random character and, consequently, they exercise as parametric noises. Moreover, the
input signal mostly consists of a useful signal, which can be taken for deterministic, and of a random additive part.
Due to interaction of additive noises with the device itself, the cross-correlation of both additive and multiplicative
noises cannot be neglected as a rule. Various combinations of noises are the origin of random and also systematic
measuring errors which can have under certain circumstances a cumulative character. Their influence deteriorates
the output signal quality and can lead finally to the stochastic stability loss. These effects can be theoretically
described using differential systems with stochastic coefficients and a stochastic right hand side considering all
input and output processes to be of the Markov type. A direct investigation of the relevant Fokker-Planck equation
is employed as the main tool. Two first stochastic moments (mathematical mean value and variance) as evolutionary
processes are investigated for a general deterministic useful signal and subsequently for two special cases of this
one. Both types of input random noises are considered. Conditions of stochastic stability with respect to intensities
of input random processes are formulated. The probability density function is deduced as well, in order to illustrate
the probabilistic character of the system response as a whole. The stochastic asymmetry of the output signal is
identified. Limitation procedures show a smooth transition from a general stochastic problem to deterministic noise
free input signal and its processing2019-01-01T00:00:00ZNáprstek, JiříFisher, CyrilComputational study of a novel valveless design of a macroscale piston pumpMachů, TomášPochylý, FrantišekŠulc, Janhttp://hdl.handle.net/11025/348142021-09-22T08:43:21Z2019-01-01T00:00:00ZNázev: Computational study of a novel valveless design of a macroscale piston pump
Autoři: Machů, Tomáš; Pochylý, František; Šulc, Jan
Abstrakt: This paper deals with a novel valveless piston pump, which is using modified Venturi diodes as a replacement for common check valves. The pump characteristic was obtained from CFD simulations in ANSYS Fluent software. The simulations were carried out on a simplified 2D geometry model of the pump. The dependencies of the volumetric efficiency of the pump on parameters of piston motion (frequency and amplitude) and backpressure are the results of the simulations. The principle of the pump is based on different rates of dissipation in the discharge and the suction diode. The paper also presents a qualitative analysis of dissipation function for turbulent flow, which provides further insight into the principle of valveless pumping.2019-01-01T00:00:00ZMachů, TomášPochylý, FrantišekŠulc, JanHelmet to head coupling by multi-body systemHynčík, LuděkBońkowski, Tomaszhttp://hdl.handle.net/11025/348132021-09-22T08:43:21Z2019-01-01T00:00:00ZNázev: Helmet to head coupling by multi-body system
Autoři: Hynčík, Luděk; Bońkowski, Tomasz
Abstrakt: The number of fatalities proves that traffic accidents and their consequences are still a serious problem to be solved. Almost half of the people dying on the world’s roads are pedestrians, cyclists, and two-wheeler riders, which are together called vulnerable road users. Future challenges such as multi-modal transport including autonomous cars and other modes of transport bring additional safety issues to be investigated. New impact scenarios, covering multi-directional impacts, can be hardly assessed using hardware dummies. Hence, the numerical simulation using human body models is the technology to be addressed for future safety assessment. Especially for vulnerable road users, the complex dynamical loading must be taken into account. Long impact scenarios with complex loading usually cost a lot of calculation time. The presented work contributes to the numerical assessment of two-wheeler riders’ safety with a further view of the optimization of personal protective equipment. For running plenty of impact scenarios for optimization of the personal protective equipment, the short calculation time is necessary. The paper presents a multibody model of a helmeted two-wheeler rider, which results in a short calculation time for assessing complex impact scenarios. The previously developed and validated human body model is addressed and it is coupled to a helmet model using the multibody system approach. The helmeted human body model is validated in oblique impact scenarios by comparing the results to an existing finite element human body model.2019-01-01T00:00:00ZHynčík, LuděkBońkowski, Tomasz