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Computational study of mesh-structured triboelectric generators
(2025-06-10) Verners, Osvalds; Bajer, Jan; Hadaš, Zdeněk; Gaidukovs, Sergejs
Triboelectric generators (TEGs) are vital for transforming mechanical energy into electrical power, facilitating the creation of self-powered devices that minimise reliance on traditional power sources. Furthermore, most typical TEGs are limited to simple 2D forms and films, limiting their potential applications. We have focused on developing 3D architectures with volumetric triboelectric dipoles to solve this. To this end, two polymeric materials with different triboelectric properties were employed for the designing of 3D architectures and the optimisation of all-polymer TEG performance. Our simplified design eliminates the integration of internal electrodes in a 3D structure. This study paves the way towards volumetric 3D TEG architectures for improved mechanical energy harvesting.
Study of micro structural material changes after WEDM based on TEM lamella analysis
(MDPI, 2020-06-07) Mouralová, Kateřina; Zahradníček, Radim; Beneš, Libor; Prokeš, Tomáš; Hrdý, Radim; Fries, Jiří
Wire electrical discharge machining is an unconventional machining technology that is crucial in many industries. The surface quality of the machined parts is carefully monitored, but the condition of the subsurface layer also plays a crucial role, especially in case of defects occurrence such as cracks or burnt cavities. The subsurface layer of individual materials is affected differently due to wire electrical discharge machining. For this reason, this study was carried out focusing on a detailed analysis of transmission electron microscope (TEM) lamellae made of Ti-6Al-4V titanium alloy, AlZn6Mg2Cu aluminium alloy, pure molybdenum, Creusabro 4800 steel, and Hardox 400 steel. The attention was first of all paid to the concentration and distribution of individual elements in the recast layer and also in the base material, which was often affected by Wire electrical discharge machining. Further, a diffraction analysis was performed for each TEM lamella in the adhesive area and in the area of the base material. In order to assess the macro-effects on the machined material, the analysis of the topography of the machined surfaces and the morphology analysis were performed using electron microscopy.
Optimal control of combined heat and power station operation
(Springer Nature, 2023-09-13) Kůdela, Jakub; Suja, Jerguš; Šomplák, Radovan; Pluskal, Jaroslav; Hrabec, Dušan
Combined heat and power stations have become one of the most utilized units of district heating systems. These stations usually contain several boilers for burning fossil fuels and renewable resources used for heating up steam, which can be used either for residential and commercial heating or electricity generation. To ensure efficiency, a boiler should either run continuously (for at least a given period) on a power output higher than a given threshold or switch off. The optimal control of the plant operations should combine an efficient setup for the turbine and boilers in operation, reflecting the demand for steam and the price of electricity, and a schedule that describes which boilers should be in operation at a given time. This paper proposes a method for optimal control of combined heat and power station operation for a given time horizon. The method is based on a two-level approach. The lower-level models correspond to finding the optimal setup of the combined heat and power station parameters for an hourly demand for different kinds of steam. The upper-level model corresponds to the optimal schedule of the operations of the individual boilers, which is planned for the entire time horizon. The lower-level model is modeled as a mixed-integer linear programming problem and is solved using parametric programming. A dynamic programming algorithm solves the upper-level model with a rolling horizon. The validity of the proposed method and its computational complexity for different granularity of the time horizon, different ranges of the parameters, varying demand for various kinds of steam, and varying electricity prices are investigated in a case study. The presented approach can be readily applied to other control problems with a similar structure.
Project Management in European Structural and Investment Funds Financed Projects in the Czech Republic
(University of Hradec Králové, 2023-04-11) Košťálová, Jana; Doskočil, Radek; Širáňová, Lenka; Lacko, Branislav
Support from European structural and investment funds has a large impact and significantly contributes to the reduction of differences between regions within the European Union. In the case of the Czech Republic the European Union helped from 2004 to 2021 to development of the country with amount of 1,700 billion CZK. This support is mainly offered in the form of subsidies by which individual projects have been supported. 164,537 projects have been implemented in the period from 2004 to the end of the year 2021. In such case of large number of projects financed from public resources is appropriate to manage them effectively and finished successfully. International standards of project management recommend the useful methods, tools and procedures leading to higher efficiency and success. The main goal of the article is to evaluate the knowledge and usage of project management international standards in the organizations implementing the projects financed or co-financed from European structural and investment funds. 171 respondents mainly project managers of this type of projects answer in questionnaire survey. They hardly know international project management standards, and if they do know them, they hardly use them in practice, with the exception of the PRINCE2 methodology, in which they have some certified employees.
The Assignment Problem and Its Relation to Logistics Problems
(MDPI, 2022-10-16) Šeda, Miloš
The assignment problem is a problem that takes many forms in optimization and graph theory, and by changing some of the constraints or interpreting them differently and adding other constraints, it can be converted to routing, distribution and scheduling problems. Showing such correlations is one of the aims of this paper. Some of the derived problems having exponential time complexity, the question arises of their solvability for larger instances. Instead of the traditional approach based on the use of approximate or stochastic heuristic methods, we focus here on the direct use of mixed integer programming models in the GAMS environment, which is now capable of solving instances much larger than in the past and does not require complex parameter settings or statistical evaluation of the results as in the case of stochastic heuristics because the computational core of software tools, nested in GAMS, is deterministic in nature. The source codes presented may be an aid, because this tool is not yet as well known as the MATLAB Optimisation Toolbox. Benchmarks of the permutation flow shop scheduling problem with informally derived MIP model and the travelling salesman problem are used to present the limits of the software’s applicability.

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