Cyclotron Resonance Study of the Two-Dimensional Electron Layers and Double-Layers in Tilted Magnetic Fields

The far-infrared absorption in two-dimensional electron layers subject to magnetic field of general orientation was studied theoretically. The Kubo formula is employed to derive diagonal components of the magneto-conductivity tensor of two-dimensional electron single-layers and double-layers. The parabolic quantum well is used to model a simple single-layer system. Both single-layer and double-layer systems can be realized in a pair of tunnel-coupled, strictly two-dimensional quantum wells. Obtained results are compared to experimental data.Comment: 4 pages, 6 figures, elsart/PHYEAUTH macros; presented on the EP2DS-15 Conference in Nara, Japan. To be published in Physica

Localization of nodes in Internet using Lighthouses system

Tato práce se zabývá problematikou lokalizace stanic v Internetu pomocí umělých souřadnicových systémů. Tyto systémy slouží k odhadu hodnoty zpoždění RTT mezi jednotlivými stanicemi. Odhadovaná hodnota zpoždění může stanici sloužit např. k efektivnímu výběru druhé stanice pro komunikaci mezi dvěma stanicemi, bez nutnosti měření těchto hodnot, což snižuje zatížení sítě. V první části této práce je vysvětlena problematika systémů pro predikci zpoždění, kde jsou teoreticky vysvětleny metody Vivaldi, King, GNP a Lighthouses. Po vysvětlení uvedené problematiky jsou v další části této práce nastíněny základní informace o prostředí, ve kterém má být vybraná metoda realizována. V poslední části práce je pak popsána metoda Lighthouses a program navržený pro použití v experimentální síti PlanetLab s následným zhodnocením dosahované přesnosti odhadu.The thesis is focused on the localization of stations in the Internet with the help of artificial coordinate systems. These systems can be used to estimate the delay value of RTT between individual stations. The estimated delay value can e.g. help the station to choose an optimal second station for communication between two stations without the necessity to measure these values, which reduces the load of the net. The first part of the thesis describes systems that predict the delay and explains how the methods Vivaldi, Kings, GNP and Lighthouses work. The next part of the work gives basic information about environment where the chosen method shall be implemented. The final part defines both the Lighthouses method and a program designed to be used in the experimental PlanetLab network and it also evaluates achieved accuracy of the estimation.

Capacitance of Gated GaAs/AlGaAs Heterostructures Subject to In-plane Magnetic Fields

A detailed analysis of the capacitance of gated GaAs/AlGaAs heterostructures is presented. The nonlinear dependence of the capacitance on the gate voltage and in-plane magnetic field is discussed together with the capacitance quantum steps connected with a population of higher 2D gas subbands. The results of full self-consistent numerical calculations are compared to recent experimental data.Comment: 4 pages, Revtex. 4 PostScript figures in an uuencoded compressed file available upon request. Phys. Rev.B, in pres

Wheelwrighting today: transformation and sustainability of the craft in Central Europe (an example of Czechia, Slovakia and Poland)

The study deals with the transformation and current form of wheelwrighting in three Central European countries - the Czech Republic, Poland, and Slovakia.  The introductory section informs about the research on the theme in the above territory, and using the example of the range of products, manufacturing technology and producers, it points out that traditional crafts can exist even today without maintaining their viability artificially. However, the text also takes into consideration how the craft has developed recently, and while evaluating its viability the author argues that the sustainability of wheelwrighting is affected not only by the economic purpose, but it is also its entertaining and tourist role and the nostalgia that begin to prove successful in addition to the former purely financial aspect. The original financial aspect shifts from the use of the wheelwright´s products for transport and livelihood to the modern use of tradition and heritage concept in business, especially in emphasizing the symbolic value of the products of traditional craftsmanship for both the producer and the consumer. Moreover, it is not only the vision of economic profit but also the element of remembering and evoking the past that are being pursued. Institutional protection of wheelwright's trade is equally important for the existence and sustainability of the craft.The study deals with the transformation and current form of wheelwrighting in three Central European countries - the Czech Republic, Poland, and Slovakia.  The introductory section informs about the research on the theme in the above territory, and using the example of the range of products, manufacturing technology and producers, it points out that traditional crafts can exist even today without maintaining their viability artificially. However, the text also takes into consideration how the craft has developed recently, and while evaluating its viability the author argues that the sustainability of wheelwrighting is affected not only by the economic purpose, but it is also its entertaining and tourist role and the nostalgia that begin to prove successful in addition to the former purely financial aspect. The original financial aspect shifts from the use of the wheelwright´s products for transport and livelihood to the modern use of tradition and heritage concept in business, especially in emphasizing the symbolic value of the products of traditional craftsmanship for both the producer and the consumer. Moreover, it is not only the vision of economic profit but also the element of remembering and evoking the past that are being pursued. Institutional protection of wheelwright's trade is equally important for the existence and sustainability of the craft

Inter-layer Hall effect in double quantum wells subject to in-plane magnetic fields

We report on a theoretical study of the transport properties of two coupled two-dimensional electron systems subject to in-plane magnetic fields. The charge redistribution in double wells induced by the Lorenz force in crossed electric and magnetic fields has been studied. We have found that the redistribution of the charge and the related inter-layer Hall effect originate in the chirality of diamagnetic currents and give a substantial contribution to the conductivity.Comment: 7 RevTex pages, 4 figures, appendix added and misprint in Eq. (11) correcte

Longitudinal conductivity and transverse charge redistribution in coupled quantum wells subject to in-plane magnetic fields

In double quantum wells electrons experience a Lorentz force oriented perpendicular to the structure plane when an electric current is driven perpendicular to the direction of an in-plane magnetic field. Consequently, the excess charge is accumulated in one of the wells. The polarization of a bilayer electron system and the corresponding Hall voltage are shown to contribute substantially to the in-plane conductivity.Comment: 3 pages, 2 figure

Selected aspects of financial risks of SMEs in Czech Republic and Slovakia

The article examines the selected aspects of financial risk of SMEs in the Czech Republic and Slovakia. Significant attributes of financial risks are defined and attitudes of entrepreneurs to risk are compared. Czech entrepreneurs were less critical in the opinion that SMEs have difficulties in gaining access to external sources of financing. It was found that only a small part of entrepreneurs in both countries can properly manage financial risks. The biggest differences are observed between these countries during the comparison of the impacts on financial risks’ growth and SMEs’ approach to external financing sources. Czech entrepreneurs have more positive attitude than the Slovak ones. Some differences were also found among the attitudes of companies in terms of their age, older companies in both countries more intensively perceive the importance of financial risks during crisis. © Ludmila Kozubikova, Aleksandr Kljucnikov, Lubos Smrcka, 2016

Cyclotron effective mass of 2D electron layer at GaAs/AlGaAs heterojunction subject to in-plane magnetic fields

We have found that Fermi contours of a two-dimensional electron gas at \rmGaAs/Al_xGa_{1-x}As interface deviate from a standard circular shape under the combined influence of an approximately triangular confining potential and the strong in-plane magnetic field. The distortion of a Fermi contour manifests itself through an increase of the electron effective cyclotron mass which has been measured by the cyclotron resonance in the far-infrared transmission spectra and by the thermal damping of Shubnikov-de Haas oscillations in tilted magnetic fields with an in-plane component up to 5 T. The observed increase of the cyclotron effective mass reaches almost 5 \% of its zero field value which is in good agreement with results of a self-consistent calculation.Comment: 4 pages, Revtex, figures can be obtained on request from [email protected]; to appear in Phys. Rev. B (in press). No changes, the corrupted submission replace