Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Fuzzy logic. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Accurate fault impedance locating algorithm

Abstract: Fault resistances affect the accuracy of short-circuit location, when distance to the fault is determined by means of measuring reactance at one end of the transmission line. This is because the current which flows through the fault resistance is slightly shifted in phase with respect to the current measured at the end of the line in question, due to the effect of the prefault load current. As a result, the fault resistance is recognised as an apparent impedance with both resistive and reactive components. The latter produces an error in the fault location, as it affects the measured reactance. The paper presents a simple algorithm which compensates for the error, and makes it possible to locate short circuits accurately; even if fault resistances are comparatively high.

Laser-induced white-light emission from graphene ceramics–opening a band gap in graphene

Abstract: Graphene ceramics can have their band gaps opened and emit white light when excited by visible or infrared light, report scientists in Poland. Wieslaw Strek and co-workers from the Polish Academy of Sciences and Wroclaw University of Technology say that the broadband emission is centred at 650 nm and has an intensity that is strongly influenced by the excitation laser power with a clear threshold. Their analysis suggests that the origin of the emission is entirely electronic in nature and is not related to incandescence or blackbody radiation. White-light emission is observed for cryogenically cooled samples with temperatures as low as 10 K. The graphene ceramic was fabricated by placing graphene flakes in a calcium carbonate toroid and subjecting them to a high temperature (550 °C) and a pressure of 8 GPa for 1 min.

Excitonic absorption in gate-controlled graphene quantum dots

Abstract: We present a theory of excitonic processes in gate controlled graphene quantum dots. The dependence of the energy gap on shape, size, and edge for graphene quantum dots with up to a million atoms is predicted. Using a combination of tight-binding, Hartree-Fock and configuration interaction methods, we show that triangular graphene quantum dots with zigzag edges exhibit optical transitions simultaneously in the terahertz, visible and UV spectral ranges, determined by strong electron-electron and excitonic interactions. The relationship between optical properties and finite magnetic moment and charge density controlled by an external gate is predicted.