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The use of thermography in surveys of monuments
Valach, Jaroslav ; Eisler, Marek
Thermography expands the portfolio of methods that can be used to study the properties of objects in the surrounding world. As recently as a decade ago, the technology was frowned upon for potential military applications controlled, which limited competition in the offer of products and manufacturers and led to high prices of devices based on these principles. It was only thanks to the release of this control that it happened to expand production and make simplified products available to mass use, so get it today for example, a customer can purchase a smartphone with an additional thermographic module for only with a small price increase. Together with the availability of equipment, we observe an increase in the application of thermography in many areas, including surveys of buildings and monuments.
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Conductive open-cell silicone foam for modulatable damping and impact sensing applications
Preuer, R. ; Šleichrt, Jan ; Kytýř, Daniel ; Graz, I.
Nature has long served as a source of inspiration for the development of new materials, with foam-like structures in fruits such as oranges and pamelos serving as examples of efficient energy dissipation. In this study, we present the synthesis and characterization of a conductive silicone foam for potential impact sensing applications. By blending Sylgard 184 and Carbon Black, we create a highly porous structure capable of dissipating energy and modulating its resistance. To investigate the properties of the foam, we utilized both micro-computer tomography (μCT) and scanning electron microscopy (SEM) imaging techniques. The μCT imaging revealed the intricate pore network of the foam, reminiscent of the complex structure found in natural sponges. SEM imaging allowed for observation of the uniform distribution of Carbon Black particles within the foam, enabling the conductive properties of the foam. The foam’s mechanical behavior was characterized by a compression test under μCT imaging to measure the deformation behavior and changes in the foam’s resistance. Additionally, a ball drop test was conducted to investigate the foam’s damping behavior while simultaneously measuring the impact location by the local change in resistance. Remarkably, our results demonstrate the exceptional damping capabilities of the conductive silicone foam, with the damping ratio modulated by adjusting the degree of compression-induced deformation. This is attributed to the collapse of the foam’s porous structure, resulting in a significant increase in the foam’s contact area. Overall, our study provides valuable insights into the behavior of conductive silicone foams and their potential as an impact sensing material. The use of both CT and SEM imaging techniques allows for a comprehensive understanding of the foam’s properties, which can be optimized for a variety of applications. The foam’s ability to modulate its damping properties by adjusting the degree of deformation provides a promising avenue for future research in the field of materials science and engineering.
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Laboratory X-ray imaging in material sciences
Koudelka_ml., Petr ; Kytýř, Daniel ; Jiroušek, O.
In recent decades, X-ray imaging and computed (micro)tomography (XCT) in particular have become common tools for volumetric inspection, visualization, and analysis of internal structure in materials from various fields [1]. In this lecture, we will explore various applications of laboratory X-ray imaging chains utilizing the combination of tomographical imaging with mechanical, thermal, or chemical loading of the irradiated sample in a so-called time-resolved imaging allowing for unprecedented insight into different phenomena driving fundamental processes encountered in various fields of material science. We will show that failure processes in engineering or geological materials [2] can be thoroughly studied by synergy of information from radiographical imaging and other methods including acoustic emission detection and optical measurements via high-speed visible-spectrum and thermal-imaging cameras, where the radiography provides important spatial information regarding deformation processes evolving within the tested samples that could not be obtained otherwise. The state-of-the-art the laboratory based imaging chains for investigation of dynamic response of materials under loading will be also discussed including high speed X-ray radiography utilizing a powerful X-ray source during high velocity impact as an approach suitable for inspection of an impacted sample. As an alternative to both conventional high-power sources and accelerator facilities, capabilities of a flash X-ray system developed primarily for in-situ ballistics research providing very short bursts of an extremely powerful intermittent X-ray radiation with a typical duration of dozens of nanoseconds will be shown.
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Identification of quasiperiodic processes in the vicinity of the resonance
Fischer, Cyril ; Náprstek, Jiří
In nonlinear dynamical systems, strong quasiperiodic beating effects appear due to combination of self-excited and forced vibration. The presence of symmetric or asymmetric beatings indicates an exchange of energy between individual degrees of freedom of the model or by multiple close dominant frequencies. This effect is illustrated by the case of the van der Pol equation in the vicinity of resonance. The approximate analysis of these nonlinear effects uses the harmonic balance method and the multiple scale method.
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Monitoring the condition of the archaeological sites of Prague Castle
Válek, Jan ; Kozlovcev, Petr ; Kotková, Kristýna ; Fialová, Anna ; Svorová Pawełkowicz, Sylwia ; Frankl, Jiří
In order to study microclimatic conditions, monitoring of selected archaeological terrains of Prague Castle was carried out in the period from August 2020 to May 2023. The internal climate of the area under the third courtyard of Prague Castle, also called Great Excavations, was monitored in the given time range. During the monitoring campaign, sensors were also placed in the area of the Small Excavations and the archaeological terrain of St. George's Monastery at various times. In particular, relative humidity, air and materials temperatures, moisture content of building materials, etc. were monitored. Samples of building materials were also taken and analysed, and the presence of biological degradation agents was monitored. The research focused in detail on describing the temperature and relative humidity of the indoor environment in relation to the moisture content of the materials and their potential degradation agents. These are primarily represented here by water-soluble salts. Their hazardousness in terms of damage to historic materials is influenced by variations in relative humidity and evaporation of water from capillary pores in combination with temperature. Research has shown that the most significant problem for sites is flooding or water seepage through the ground, surrounding structures or ceiling.
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