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Possibilities and pitfalls of revitalizing the timber structure of an industrial building from the 19th century from the viewpoint of diagnosis
(IOP Publishing, 2018-07-16) Heřmánková, Věra; Anton, Ondřej; Cikrle, Petr; Komárková, Tereza; Stehlík, Michal
A typical feature of contemporary cities is the permanent shortage of land suitable for residential development inside the city. This leads to attempts in recent years to re-use the so-called Brownfields which have the appearance of the former industrial areas, the buildings of which are mostly far beyond the estimated lifetime. Apart from the standard procedure, i.e. demolition and new construction, it is possible to come across efforts, in recent years, to renovate and newly utilize the existing industrial buildings, some of which have a historical value and considerable design potential for an alternative use. The paper presents a case where an original five-story warehouse building from the mid-19th century should be prospectively used for residential purposes, while maintaining and utilizing, for aesthetic purposes, the timber ceiling structures. The paper describes the procedure of diagnosis of a timber structure and its results, suggesting potential risks of similar renovations where the object of interest has not been used and maintained for a long period of time.
Experimental testing of the electromagnetic coil – determining the range of electromagnetic coil
(IOP Publishing, 2018-07-16) Komárková, Tereza; Láník, Jaromír; Anton, Ondřej; Heřmánková, Věra
The principle of steel fibre reinforced concrete structures is a uniform distribution of steel fibers in the given volume (structure or structural element), which, however, is not always possible to guarantee in the production. This is closely related to a problem of performing diagnosis of the existing steel fibre reinforced concrete structures. Despite the fact that this material is not unknown, in the standards regulating quality control of the uniformity of fibre distribution, the assessment of distribution uniformity is still based on a destructive testing method. The paper describes a partial experiment which consisted in testing a proposed measuring device and in determining the depth of electromagnetic field range in the test specimens.
There Are No Conformal Einstein Rescalings of Pseudo-Riemannian Einstein Spaces with n Complete Light-Like Geodesics
(MDPI, 2019-09-01) Hinterleitner, Irena; Mikeš, Josef; Guseva, Nadezda
In the present paper, we study conformal mappings between a connected n-dimension pseudo-Riemannian Einstein manifolds.
Compatibility of Phase Change Materials and Metals:Experimental Evaluation Based on the Corrosion Rate
(MDPI, 2020-06-18) Ostrý, Milan; Bantová, Sylva; Struhala, Karel
The construction and maintenance of building stock is responsible for approximately 36% of all CO(2)emissions in the European Union. One of the possibilities of how to achieve high energy-efficient and decarbonized building stock is the integration of renewable energy sources (RES) in building energy systems that contain efficient energy storage capacity. Phase Change Materials (PCMs) are latent heat storage media with a high potential of integration in building structures and technical systems. Their solid-liquid transition is specifically utilized for thermal energy storage in building applications. The typically quite old example is the use of ice that serves as long-term storage of cold. Large pieces of ice cut in winter were stored in heavily insulated spaces and prepared for cooling of food or beverages in summer. In the contemporary use of the principle, the PCMs for building applications and tested in this study must have a melting range close to the desired temperature in the occupied rooms. As the PCMs need to be encapsulated, several types of metal containers have been developed and tested for their thermal conductivity and resistance to mechanical damage, which enhances the performance of these so-called latent heat thermal energy storage (LHTES) systems. Long-term compatibility of metals with PCMs depends, i.e., on the elimination of an undesirable interaction between the metal and the specific PCM. Heat storage medium must be reliably sealed in a metal container, especially if the LHTES is integrated into systems where PCM leaks can negatively affect human health (e.g., domestic hot water tanks). The aim of this study is to evaluate the interactions between the selected commercially available organic (Linpar 17 and 1820) and inorganic (Rubitherm SP22 and SP25) PCMs and metals widely used for PCM encapsulation (aluminum, brass, carbon steel, and copper). The evaluation is based on the calculation of the corrosion rate (CR), and the gravimetric method is used for the determination of the weight variations of the metal samples. The results show good compatibility for all metals with organic PCMs, which is demonstrated by a mass loss as low as 2.1 mg in case of carbon steel immersed in Linpar 1820 for 12 weeks. The exposure of metals to organic PCMs also did not cause any visual changes on the surface except for darker stains, and tarnishing occurred on the copper samples. More pronounced changes were observed in metal samples immersed in inorganic PCMs. The highest CR values were calculated for carbon steel exposed to inorganic PCM Rubitherm SP25 (up to 13.897 mg center dot cm(-2)center dot year(-1)). The conclusion of the study is that aluminum is the most suitable container material for the tested PCMs as it shows the lowest mass loss and minimal visual changes on the surface after prolonged exposure to the selected PCMs.
A dynamical system with random parameters as a mathematical model of real phenomena
(MDPI, 2019-10-30) Diblík, Josef; Dzhalladova, Irada; Růžičková, Miroslava
In many cases, it is difcult to nd a solution to a system of difference equations with random structure in a closed form. Thus, a random process, which is the solution to such a system, can be described in another way, for example, by its moments. In this paper, we consider systems of linear difference equations whose coefcients depend on a random Markov or semi-Markov chain with jumps. The moment equations are derived for such a system when the random structure is determined by a Markov chain with jumps. As an example, three processes: Threats to security in cyberspace, radiocarbon dating, and stability of the foreign currency exchange market are modelled by systems of difference equations with random parameters that depend on a semi-Markov or Markov process. The moment equations are used to obtain the conditions under which the processes are stable.

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