Model vrtulové pohonné jednotky s variabilním úhlem náběhu

The contribution deals with the mathematical model of the propeller drive unit with variable pitch. The introductory part of the article aims at a general mathematical description of the internal structure of the aircraft propulsion. The DC motor and propeller model are presented in next chapter. The last part presents the comparison between MatLab Simulink model and experimental laboratory stand of variable pitch drive unit. Variable pitch propeller drive is useful to minimize power consumption. The use of these units for the drones is only experimental in terms of optimization of energy consumption.V tomto článku je popsán matematický model vrtulové pohonné jednotky s variabilním úhlem náběhu vrtulových listů (VPPU). V úvodní části článku je popsán základní matematický model celé pohonné jednotky. V další části je popsán model motoru ve vazbě s vrtulí. V závěru článku je prezentován výstup simulací v MatLab Simulink v porovnání s výstupy s laboratorního standu. Význam VPPU je v možné úspoře energie letounu. Využití těchto jednotek pro pohon dronů za účelem snižování spotřeby energie je v současnosti jen na experimentální úrovni

Simulace svařování tenkostěnného potrubí

The presented paper deals with the residual stress after a welding operation performed by using the TIG method. It was necessary to determine whether or not tension plays a major role in the distortion of the geometry of a thin-walled pipe, or in other words, whether the drawing dimension of the ovality exceeds the specified tolerance. The result of this simulation will help to determine whether or not designers will have to find another technological solution to complete parts. The assembly consists of three parts: the weld bead, thin-walled pipe, and hoop, which are connected by welds as a final product.Předložena práce se zabývá zbytkovým napětím po svařování pomocí metody TIG. Bylo nutné určit zda–li toto napětí hraje hlavní roli v pokřivení geometrie tenkostěnného potrubí či nikoliv. Jinak řečeno, zda-li rozměry ovality překračují stanovenou výkresovou toleranci či nikoliv. Výsledek této simulace pomůže konstruktérům rozhodnout, budou-li muset najít jiné technologické řešení pro zkompletování dílců či nikoliv. Sestava tvoří tři části: svarová housenka, tenkostěnné potrubí a obruč, které jsou navzájem spojeny svary jako finální product, see Fig. 3

Geophysics for underground engineering

The growth of underground engineering brought a need for the use of geophysical methods for research of underground constructions rather different in approach compared to that of civil engineering. These changes relate to surface measurement on the one hand and the development of new specialised methods used for underground work on the other. The results of a complete documentation of mining work, the application of the resistivity methods used underground and also the use of 3D electrical resistivity tomography, are all presented here

Das IÖW/future-Ranking der Nachhaltigkeitsberichte

Alle zwei Jahre bewerten das Institut für ökologische Wirtschaftsforschung und die Unternehmerinitiative „future – verantwortung unternehmen“ die Nachhaltigkeitsberichterstattung deutscher Unternehmen. Im achten IÖW/future-Ranking wurden Ende Februar die Preisträger gekürt

Towards Understanding the Formation of Continuous IT Use

The benefit of IT comes from the continuing use, not its initial adoption. Compared to the amount of research done on IT adoption, insights on why users continue to use IT systems are sparse. Nevertheless, there are publications with promising ideas and findings aiming to explain continuous use. This paper reviews and synthesizes the current research to examine whether a combination of previous results will lead to a better understanding on the formation of continuous IT use. Further, the current theoretical and methodological shortcomings are exposed and addressed by the derived research design. As study context, we use the implementation of a web based application for students. We focus on a longitudinal study that includes three measurements over an eleven week period. To measure the actual usage of participants, we combine self-reported and computer-recorded data. The study is currently running, with over 300 participants registered

Geophysics for underground engineering

The growth of underground engineering brought a need for the use of geophysical methods for research of underground constructions rather different in approach compared to that of civil engineering. These changes relate to surface measurement on the one hand and the development of new specialised methods used for underground work on the other. The results of a complete documentation of mining work, the application of the resistivity methods used underground and also the use of 3D electrical resistivity tomography, are all presented here

Charge conservation breaking within generalized master equation description of electronic transport through dissipative double quantum dots

We report an observation of charge conservation breaking in a model study of electronic current noise of transport through a dissipative double quantum dot within generalized master equation formalism. We study the current noise through a double quantum dot coupled to two electronic leads in the high bias limit and a dissipative heat bath in the weak coupling limit. Our calculations are based on the solution of a Markovian generalized master equation. Zero-frequency component of the current noise calculated within the system, i.e., between the two dots, via the quantum regression theorem exhibits unphysical negative values. On the other hand, current noise calculated for currents between the dots and the leads by the counting variable approach shows no anomalies and seems physically plausible. We inquire into the origin of this discrepancy between two nominally equivalent approaches and show that it stems from the simultaneous presence of the two types of baths, i.e., the electronic leads and the dissipative bosonic bath. This finding raises interesting questions concerning conceptual foundations of the theory describing multiple-baths open quantum systems widely encountered in nanoscience.Comment: 10 pages, 4 figures; submitted to Physica E as proceedings of FQMT0

A method for measuring the quality of graphic transfer to materials with variable dimensions (wood)

The transfer of graphics to a product's surface is a widely known technology. Printing, engraving, and etching are used every day in production processes with countless types of materials. This paper deals with quality control for laser engraving on surfaces with variable dimensions via optical sensors. The engraving process, apart from colour changes, can induce volume and moisture changes, which lead to dimension changes in some materials. Natural materials and biomaterials are among the ones most affected. Combined with the porous and inhomogeneous structure of such a material, it can be difficult to measure the quality of graphic transfer, especially for shaded products. The quality control of laser-engraved photographs on thin layers of wood veneer was selected as a suitable problem to solve. A complex method for the quality measurement of the specified production was designed and tested. We used an affine transformation to determine the system behaviour and to determine the transfer function of material changes during the production process. Moreover, there is a possibility to compensate the image deformation of the engraved product.Web of Science2216art. no. 603