Brno University of Technology

About: Brno University of Technology is a education organization based out in Brno, Czechia. It is known for research contribution in the topics: Computer science & Fracture mechanics. The organization has 6339 authors who have published 15226 publications receiving 194088 citations. The organization is also known as: Vysoké učení technické v Brně & BUT.

Conceptual design of a selectable fractional-order differentiator for industrial applications

Abstract: In the past decade, researchers working on fractional-order systems modeling and control have been considering working on the design and development of analog and digital fractional-order differentiators, i.e. circuits that can perform non-integer-order differentiation. It has been one of the major research areas under such field due to proven advantages over its integer-order counterparts. In particular, traditional integer-order proportional-integral-derivative (PID) controllers seem to be outperformed by fractional-order PID (FOPID or PIλDμ) controllers. Many researches have emerged presenting the possibility of designing analog and digital fractional-order differentiators, but only restricted to a fixed order. In this paper, we present the conceptual design of a variable fractional-order differentiator in which the order can be selected from 0 to 1 with an increment of 0.05. The analog conceptual design utilizes operational amplifiers and resistor-capacitor ladders as main components, while a generic microcontroller is introduced for switching purposes. Simulation results through Matlab and LTSpiceIV show that the designed resistor-capacitor ladders can perform as analog fractional-order differentiation.

Multicaloric effect in a solid: New aspects

Abstract: The multicaloric effect that is the result of interaction between various caloric effects has been studied theoretically. The effects attributable to the pairwise interactions of fields (piezomagnetocaloric, piezoelectrocaloric, and magnetoelectrocaloric effects) have been added to the previously known electrocaloric, magnetocaloric, and elastocaloric effects that exist when the electric, magnetic, and elastic fields change. These new effects are shown to be determined by the temperature dependence of the piezomagnetic (magnetostrictive), piezoelectric (electrostrictive), and magnetoelectric coefficients. According to the estimates obtained, the change in entropy in an isothermal process under the magnetoelectrocaloric effect for Cr2O3 is 2–5 mJ kg−1 K−1. The caloric effects caused by the influence of the gradient in one of the fields on other fields are shown to contribute to the multicaloric effect. One of these gradient effects, the flexocaloric one, which consists in a change in temperature and/or entropy when a strain gradient is applied or removed, has been studied in detail as an example. It follows from the derived formulas that the greatest values of this effect should be expected for materials with strong temperature dependences of the flexocaloric coefficient, permittivity, or permeability. The change in temperature calculated from experimental data for a PMN ferroelectric is estimated as 2–6 mK at a strain gradient of 1 m−1. The interaction between fields of a different nature is known to lead to the synergetic effect, and the multicaloric effect can reach values that are commonly called giant ones, expanding considerably the possible domains of its application.

A novel tribological study on DLC-coated micro-dimpled orthopedics implant interface.

Abstract: This study investigates a tribological performance of diamond like carbon (DLC) coated micro dimpled prosthesis heads against ceramic cups in a novel pendulum hip joint simulator. The simulator enables determining friction coefficient and viscous effects of a concave shaped specimen interface (conformal contact). Two types of DLC such as hydrogenated amorphous carbon (a-C:H) and tetrahedral amorphous carbon (Ta-C) and one set of micro dimple (diameter of 300 µm, depth of 70 µm, and pitch of 900 µm) were fabricated on metallic prosthesis heads. The experiment results reveal a significant friction coefficient reduction to the ‘dimpled a-C:H/ceramic’ prosthesis compared to a ‘Metal (CoCr)/ceramic’ prosthesis because of their improved material and surface properties and viscous effect. The post-experiment surface analysis displays that the dimpled a-C:H yielded a minor change in the surface roughness, and generated a larger sizes of wear debris (40–200 nm sized, equivalent diameter), a size which could be certainly stored in the dimple, thus likely to reducing their possible third body abrasive wear rate. Thus, dimpled a:C–H can be used as a ‘metal on ceramic hip joint interface’, whereas the simulator can be utilized as an advanced bio-tribometer.

Control and Near-Field Detection of Surface Plasmon Interference Patterns

Abstract: The tailoring of electromagnetic near-field properties is the central task in the field of nanophotonics. In addition to 2D optics for optical nanocircuits, confined and enhanced electric fields ar...