CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
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Uranium foil neutron activation analysis
Full text linkAt the Department of Nuclear Reactors of the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University (FNSPE CTU) in Prague, there is a need to implement a neutron activation analysis as a tool for the separation of uranium foils depending on various 235U and 238U contents. Experiments were carried out on the training reactor VR-1 “Sparrow”, which is operated at the institute mentioned above. The uranium foils were analysed using the neutron activation analysis and gamma-ray spectrometry, and were separated into two groups, the first group contained foils of depleted uranium and the other contained natural uranium foils. The uranium foils can be further used for educational purposes or experimental applications, such as the measurement of neutron spectral indexes, neutron activation analysis of uranium ore, or delayed neutron analysis. The neutron activation analysis has been extended to determine whether foils contain natural or depleted uranium
Commissioning of universal Split Hopkinson Bar for dynamic compression and tension experiments
Full text linkSplit Hopkinson Bar is an experimental apparatus designed for acquiring material properties in dynamic regime. The apparatus is usually constructed as a single purpose experimental device for specific type of loading, most commonly either compression (Split Hopkinson Pressure Bar) or tension (Split Hopkinson Tensile Bar). In this paper, a simple and highly modular design capable of testing for multiple types of loading is introduced, which can be a great advantage to obtain material properties under different loading conditions. The device was successfully assembled, including its electrical installation and implementation of a pneumatic launching system and was fitted with multiple sensors. Series of calibration procedures was conducted successfuly to analyze correct behaviour of the system. After calibration, the apparatus was subjected to multiple pilot tests with samples manufactured using 3D printing. The results were compared to those obtained using the quasi-static method
ESG implementation in the construction industry according to 2022-2024 surveys
Full text linkThe transition to sustainability will gradually change the face of businesses in all sectors, not least construction. In terms of adopted EU legislation, it will have the greatest impact on their activities in less than 5 years. For companies, the adoption of sustainability principles means new business conditions, new market opportunities, the possibility of acquiring resources, but also new responsibilities. One of these is the obligation to report on ESG (information on the impact of their business on the environment, people and society). This article presents the results of ten sustainability surveys conducted between 2022 and 2024. All the data were collected using the questionnaire method. The aim of the article was to determine the willingness of companies operating in the Czech market to integrate sustainability aspects into their corporate strategies and to publish sustainability (ESG) reports based on the published results. The results show that there is currently a large gap in the level of ESG implementation not only between large and medium-sized construction companies, but also between Czech and foreign companies. The research confirms that ESG awareness or activity decreases with the size of the company. Many small and micro companies believe that ESG does not affect them. The sooner companies start reporting standardised sustainability data, the sooner and easier they will be able to access more favourable loans and financing from investors, and the sooner they will be able to contribute to the Sustainable Development Goals for Europe as a whole
PULSED FIELD ABLATION IN PATIENTS WITH CARDIAC IMPLANTABLE ELECTRONIC DEVICES - TECHNICAL ASPECTS OF INTERACTION: OBSERVATIONAL CASE STUDY
Full text linkPulsed field ablation (PFA) is a new method for treating cardiac arrhythmias. This method uses a sequence of high-voltage pulses to selectively destroy myocardial cells. The procedure can also be performed in patients with a cardiac implantable electronic device (CIED) such as a pacemaker (PCM) or an implantable cardioverter-defibrillator (ICD). The aim was to analyze such interaction of the pulse field and the pacing system. The interaction was assessed in two patients undergoing pulsed-field pulmonary vein isolation for paroxysmal atrial fibrillation in Liberec Regional Hospital. The first patient had a biventricular ICD, the CRT (cardiac resynchronization therapy) type. The second patient had a PCM, the 2D (dual-chamber) type. The signal waveform analysis was performed visually by an expert in real-time via the programmer (using real-time intracardiac electrogram) during each application of pulsed energy in the left atrium. The distance of the ablation catheter from the CIED sensing poles was <10 cm depending on the application in the left or the right pulmonary veins. On the intracardiac ECG, the interference from the PFA was detected by the device as an isolated cardiac event. In ICDs, the interference detection algorithm was also sporadically activated. There was no damage to the CIED electronics during PFA. CIED electronics is protected against high-energy pulsed fields used in these kind of interventions. Impulse interference is not a significant risk for affecting the stimulatory function of the CIED. All CIEDs have limits in signal processing as they are targeting the heart signal frequency range. The signal envelope from these high-frequency applications can be seen on the intracardiac ECGs. The signal processing parameters of CIEDs and the effect on pacing function may vary across different systems.
Simulation of wind flow around an alternative flat-roofed fortress tower ruin
Full text linkAn analysis of the effects of alternative flat roof sizes and positions on wind flow around a ruin model is presented. The modelled ruin has almost cube-like proportions, with an open roof plane and a destroyed corner. Roofs over ruins are seen as a means of protection against the wind, which is considered a destructive mechanism. The purpose of the roof as a monumental means of presentation and limits of its implementation are also discussed. Wind flow is illustrated by external pressure and skin friction coefficients. Taking their changes into account, the degree of protection flat roof alternatives provide is estimated and optimal flat roof alternatives are discussed. Simulations were carried out using the 3D Time Steady Reynolds-averaged Navier-Stokes equations and the Shear StressTransport k-ω turbulence model
The satellite SMILE – its prospects for observing cosmic sources
Full text linkWe describe the scientific potential of a Soft X-ray Imager (SXI) onboard the ESA–CAS satellite SMILE to study the activity of cosmic X-ray sources in the soft X-ray region and located in the fields planned to be observed by SXI. We used the 2–3 keV band flux of the monitor MAXI/ISS, covering at least part of the expected band of the SXI/SMILE telescope. We discuss how SXI can contribute to this branch and how combining the SXI/SMILE data with those obtained by other satellites on the same days can be helpful if the light curves of the 1-day means are used. We show these possibilities on several examples of cosmic X-ray sources (Vela X-1 and GROJ1008-57 containing neutron stars accreting matter from their companions) in the field of view of SXI. Including observations from MAXI/ISS and BAT/Swift will enable extending the coverage to the energy of 50 keV
Seismic performance evaluation of prefabricated bridge substructure connected by grouted sleeves
Full text linkIn this study, the seismic performance of prefabricated bridges connected by grouted sleeves has been evaluated. 12 sleeve specimens and 4 cast-in-place specimens with varying anchorage lengths and water-to-cementitious material ratios were fabricated to investigate the bond-slip performance by uniaxial tension test based on the constitutive relationship of grouted sleeves and bond-slip behaviour between rebar and concrete. A finite element (FE) model was proposed to analyse the prefabricated bridge substructure, considering bond and slip between rebar and sleeve. The corresponding seismic performance under simulated seismic effects was investigated using a multi-angle analysis method. Also, parametric investigation using FE analysis was performed to examine the influence of various parameters on the seismic performance of the specimens. The experiment results showed minimal bonding performance differences between the grouted sleeve specimens and the cast-in-place specimens, indicating that the grouted sleeve connection satisfies the connection performance requirements. The simulation results show that the typical damage form of the prefabricated bridge substructure connected by grouted sleeves is bending, the shape of the hysteresis loop is either shuttle or bow, with the slope of the descending section of the skeleton curve varied not significantly because of the excellent ductility. The results corroborate the excellent seismic performance of prefabricated bridge substructures connected by grouted sleeves
Mechanical properties analysis of a cable-stayed bridge without backcables under the influence of temperature and inclination angle
Full text linkCable-stayed bridge without backcables is an important branch of the cable-stayed bridge family. It tilts the bridge tower to one side and removes the cable behind it. It balances the cable force of the cable-stayed cable with its own weight. This paper relies on the construction project of the main bridge of Jinzhou Bridge, and uses finite element analysis software to establish a space model to simulate and analyze the construction process, focusing on the influence of the bridge tower inclination and temperature. When the inclination angle of the bridge tower changes within a certain range, it has little effect on the stiffness and strength of the structure, but under the condition that the stress of the tower girder is roughly the same, the greater the inclination angle of the tower, the greater the counterweight of the tower, and the greater the material consumption of the tower. Angle of the tower, the greater the counterweight of the tower, and the greater the material consumption of the tower. When the bridge tower is 52°, 55° and 58°, the stress on the left side of the bridge tower is -5.8MPa, -4.1MPa and 0.7MPa, respectively
Hybrid reinforcement of TRC from flax and AR glass
Full text linkThis article focusses on the possible use of hybrid reinforcement from inorganic and organic materials in a thin concrete plates, such as Textile-reinforced concrete. Organic materials, such as flax, jute, or sisal, have high tensile strengths. Young’s modulus is, on the other hand, problematic, so the combination with inorganic textiles goes hand in hand. Natural fibres are renewable materials, making them an environmentally friendly material, so using them as a partial substitution of inorganic materials would make concrete reinforcement more sustainable. In this article, four-point tests of hybrid reinforced concrete plates with alkali-resistant glass and flax are presented. In addition, a hybrid reinforcement cross-sectional microscopy was done to evaluate the impregnation with epoxy resin
Comparative study of different types of waterproofing screeds with a focus on radon permeability after the freeze-thaw exposure
Full text linkThis study aims to verify and independently compare the functionality of waterproofing screeds against the effect of radon with the influence of freezing cycles. The effect of freezing cycles on the sealing ability against radon was investigated on polymer, silicate (mineral), and bituminous screeds. The measured values correspond to commonly used insulation materials, confirming the correctness of the measurement and evaluation methodology. Waterproofing screeds are shown to be suitable materials for substructure applications. Unlike waterproofing made from strips such as bitumen membrane or PVC membrane, they do not contain joints and can thus offer a more reliable solution. The measured values show minimal differences between the tested waterproofing screeds after freeze-thaw exposure. Especially in the case of silicate (mineral) screed and polymer screed, the effect is negligible. The greatest effect of freeze-thaw cycles on the ability to seal against radon was observed for bitumen screeds