Ing. Kateřina Nováková

Electrochemical impedance spectroscopy (EIS) is a measurement method widely used for non-destructive analysis and diagnostics in various electrochemical fields. From the measured dependence of the battery impedance on the frequency, it is possible to determine the parameters of various equivalent electrical circuit models of the battery. The conventional method of battery measurement using single-sine EIS is currently one of the most widely used methods for the analysis of lithium-ion batteries. However, its most significant disadvantage is the relatively long measurement time. For this reason, there is a growing demand for faster methods using fast-Fourier transform or pseudo-random sequences. A description of various EIS methods applications is provided in this paper.

Fiber-reinforced concrete is a new composite material whose advantages include tensile strength or resistance to extreme loadings. The strength of the reinforcement can be further improved by orienting the fibers in a magnetic field. The orientation must be done immediately after pouring the black concrete into a form. This paper deals with the magnetic field simulation acting on a steel fiber in the Ansys Maxwell environment. The simulation examines the electromagnetic toque affecting the steel fiber based on its geometry. The model consists of a fiber inserted between Helmholtz coils. Torque curves for various fibers were monitored, and based on the results, a comparison between several commercially available fibers is presented. Furthermore, a device used for measuring the magnetization and hysteresis curves was simulated, and the results are presented in the paper

The efficiency of fibre reinforcement in concrete can be drastically increased by orienting the fibres using a magnetic field. However, the parameters of such a field are not immediately apparent, as they depend on the specific fibre reaction to the magnetic field. In this paper, numerical simulations are conducted to study the mechanical torque acting on fibres placed in a magnetic field. The simulations are verified with an experimental setup as well as theoretical relationships. Ten different fibre types, both straight and hook-ended, are examined. The developed model can be successfully used to study the behaviour of fibres in a magnetic field. The fibre size plays the most important role together with the magnetic saturation of the fibre material. Multiple fibres show significant interactions.