Impact of increasing energy efficiency of buildings on the acoustic properties of their claddings

Interdisciplinárne rezonujúcou témou v oblasti stavebnej fyziky je snaha znižovania energetickej náročnosti budov pri súčasne čo najnižšom možnom zaťažení ekosystému. Pokrok v materiálových, konštrukčných a technologických riešeniach umožňuje kontinuálne zvyšovanie kritérií na energetickú efektívnosť budov. Tu sa však ľahko môžeme stretnúť s komplikáciami v rámci konštrukčných riešení z pohľadu stavebnej akustiky ako aj s generovaním nežiadúceho hluku implementovaním technického vybavenia budov. V tomto príspevku sme sa snažili poukázať na vybrané prípady, s ktorými sa bežne môžeme stretávať v praxi. Podkladom tohto článku boli kapitoly 5.33 a 5.5 z knižne vydanej publikácie (Rychtáriková-Chmelík-Urbán, 2019).An interdisciplinary resonant topic in the field of building physics is the effort to reduce the energy intensity of buildings while at the lowest possible load on the ecosystem. Advances in material, construction and technological solutions enable the continuous increase of criteria for the energy efficiency of buildings. Here, however, we can easily encounter complications in structural solutions from the point of view of building acoustics as well as the generation of unwanted noise by implementing the technical equipment of buildings. In this paper, we have tried to point out selected cases that we can commonly encounter in practice. This article was based on Chapters 5.33 and 5.5 of the book published (Rychtáriková-Chmelík-Urbán, 2019)

The Influence of Rolling Conditions on Deformation Behavior of Magnesium Alloy Sheets

The influence of texture on deformation behavior was investigated for conventionally rolled magnesium alloy slabs and rolled twin roll cast magnesium alloy strips in the form of sheets. The Mg-Zn based sheets were deformed at room temperature with the tensile axis oriented in the rolling and transversal directions. The texture with respect to different rolling conditions was characterized by X-ray diffraction. In the case of Mg-Zn-rare earth alloy sheets, the basal pole intensity, aligned with the sheet normal direction, is lower for conventionally rolled sheet in comparison to the rolled twin roll cast strip. Difference in angular distribution of basal planes influences on the mechanical behavior of the sheets. The yield strength is higher for the tension along rolling direction than along transversal direction for the conventionally rolled sheets, whereas the opposite deformation behavior is observed for the rolled twin roll cast strips. Furthermore, the planar anisotropy of the yield strength is less pronounced for the rolled twin roll cast strips. The deformation behavior of the sheets was also investigated by the acoustic emission technique. The acoustic emission signal analysis correlates the microstructure and the stress-time curves with active deformation mechanisms. It highlights the activity of a basal slip and tensile twinning, particularly during the transverse direction tension

On the Effect of the Extrusion Speed on Microstructure and Plastic Deformation of ZE10 and ZEK100 Magnesium Alloys - an Acoustic Emission Study

Mg-Zn-based alloys ZE10 and ZEK100 have been extruded at different speeds varying from 1 m/min to 20 m/min. Specimens taken in the extrusion direction were uniaxially loaded in tension and compression at room temperature. The results are discussed using concurrent acoustic emission monitoring during mechanical testing and the acoustic emission signal analysis that correlates the microstructure and the stress-strain curves to the possible deformation mechanisms. In all tests, the acoustic emission response exhibited a large acoustic emission peak at the beginning of plastic deformation. A small local maximum on the onset of the acoustic emission activity was frequently observed, i.e. at very low stresses. For the alloys with bimodal grain structure tested in compression, an additional acoustic emission peak appeared at larger strains. This peculiar behavior can be explained by interplay of (10-12)-twinning and dislocation slip in samples with various grain size distributions

Acoustic Emission Study of the Deformation Behavior of Mg-Mn Alloys Containing Rare Earth Elements

Magnesium-manganese (Mg-Mn) based alloys with various chemical composition were processed by indirect extrusion at two different speeds. Alloying with Mn and rare earth elements has significant influence on the microstructure and on the texture of the alloys under investigation. This paper deals with the acoustic emission analysis of the deformation behavior of the extruded Mg-Mn alloys. The acoustic emission measurements were performed during the uniaxial tension and compression tests, and the obtained results are discussed with respect to the influence of rare-earth elements on the deformation behavior, particularly in terms of the activation of dislocation glide and twinning

On the Effect of the Extrusion Speed on Microstructure and Plastic Deformation of ZE10 and ZEK100 Magnesium Alloys - an Acoustic Emission Study

Mg-Zn-based alloys ZE10 and ZEK100 have been extruded at different speeds varying from 1 m/min to 20 m/min. Specimens taken in the extrusion direction were uniaxially loaded in tension and compression at room temperature. The results are discussed using concurrent acoustic emission monitoring during mechanical testing and the acoustic emission signal analysis that correlates the microstructure and the stress-strain curves to the possible deformation mechanisms. In all tests, the acoustic emission response exhibited a large acoustic emission peak at the beginning of plastic deformation. A small local maximum on the onset of the acoustic emission activity was frequently observed, i.e. at very low stresses. For the alloys with bimodal grain structure tested in compression, an additional acoustic emission peak appeared at larger strains. This peculiar behavior can be explained by interplay of (10-12)-twinning and dislocation slip in samples with various grain size distributions

Influence of Pre-Compression on Tensile Behaviour in Wrought Mg-Zn-Ce Alloy Studied by the Acoustic Emission Technique

Wrought Mg-Zn-Ce alloy (ZE10) has been pre-compressed and subsequently subjected to tensile loading. Due to a fibre texture of the samples, the level of pre-compression stress significantly influences the subsequent tensile behaviour. The acoustic emission technique was used for monitoring active deformation mechanisms during mechanical testing. The obtained acoustic emission results are correlated to the stress-time curves and the differences in the acoustic emission count rate were used to reveal changes in underlying deformation mechanisms. Firstly, a compression-tension cycle was monitored by the acoustic emission technique. Then, the samples were deformed to specific points on the stress-time curve, where acoustic emission exhibits strong changes in the activity. The following microstructure analysis of the samples, deformed to different strain-levels, by using electron back scattered diffraction method brought a detailed insight into active deformation mechanisms. Twinning during the pre-compression was followed by detwinning during the tensile loading. Two consecutive acoustic emission peaks, which appeared at larger strains, are explained by interplay of detwinning and dislocation slip and a nucleation of compression twins, respectively

Fracture surfaces of porous materials

The fracture surface of composite porous material has been investigated as a multicomponent surface onto which the volume components are projected with different dimensions. It has been shown that these fracture surfaces bear information on the value of compressive strength and may be characterized by a general dimension at least for a particular class of materials

Accumulation of cyanobacterial oxadiazine nocuolin A is enhanced by temperature shift during cultivation and is promoted by bacterial co-habitants in the culture

© 2019 Elsevier B.V. Proper setting of cultivation conditions is essential for production of high-value compounds in microbial biotechnology. The present study characterizes photoautotrophic growth and capacity to accumulate the antiproliferative secondary metabolite Nocuolin A (NoA) in cyanobacterium Nostoc sp. CCAP 1453/38. As the cyanobacterial culture was found to be non-axenic, the bacteria accompanying the culture were characterized, then the growth demands and NoA production in the Nostoc-bacterial consortium were determined, and finally an axenic strain was prepared. For the purposes of growth characterization, the culture was maintained in a quasi-continuous regime under various light intensities, temperatures, and inorganic carbon concentrations in a small-scale laboratory photobioreactor. The maximum biomass growth rate obtained was 0.10 h−1 (doubling time Dt = 6.93 h). Following optimal growth conditions were identified: temperature of 35 °C, light intensity 600 μmol(photons) m−2 s−1, and 2500 ppm CO2 in the sparging gas. As the temperature optima for the biomass production and for NoA accumulation differed, biphasic cultivation for maximal NoA yield was designed, leading to a three times more effective cultivation procedure compared to batch culture maintained at a temperature optimal for NoA production. The increased NoA accumulation at reduced temperature that correlated with enhanced expression of NoA biosynthetic genes after the temperature shift suggested its regulation occurs at the expression level. It has further been shown that NoA production is reduced in axenic culture, which indicates that it is also triggered by presence of bacteria. This study shows an example of how a biphasic cultivation mode with different temperatures can be used in high-value compound production processes. It also brings direct evidence that cyanobacterial strain axenization can lead to a rapid decrease in production of valuable compounds and that non-axenic strains may be considered more suitable for retrieval and initial production of novel pharmaceutical leads