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BIOIMPACT OF HYPOMAGNETIC FIELDS
Get PDFHypomagnetic fields (HMF), or nearly zero magnetic fields, are fields with a value of magnetic flux density lower than the Earth\u27s geomagnetic field. The effects of these so-called weak magnetic fields can manifest in living organisms by influencing biological functions such as the circadian system, calcium balance in cells, DNA methylation, concentration of reactive oxygen species, as well as changes in metabolic and developmental processes. This article describes how HMF affects selected cellular structures through specific exposure parameters, whose selective impact has been verified on the proliferative activity of the yeast strain Saccharomyces cerevisiae. In 25 experiments, the inhibitory effect of a time-varying magnetic field at a level of 0.365 µT was confirmed, which corresponds to the magnitude of magnetic flux density in the vicinity of 100 kV power lines. Global organizations also point out the possible correlation between HMF generated by 50 Hz power lines and various diseases, particularly childhood leukemia
Modelling of gasification of organic waste in thermal-plasma chemical reactors
Get PDFThe paper presents the latest numerical simulations of gasification of wood particles and sewage sludge in two different thermal-plasma chemical reactors using either a unique DC-plasma torch stabilized by argon and water vortex or DC-plasma air torches. Numerical results of gasification and syngas production from crushed wood show that high syngas content (∼90%) was achieved for all studied currents (400–600 A) and wood particle diameters (0.2 mm – 20 mm). The CO and H2 molar fractions for three different particle diameters for 400 A obtained by modelling at the exhaust outlet are in reasonably good agreement with the experimental values (CO–0.6, H2–0.3). The gasification of sewage sludge by air plasma torches generate syngas of a lower quality (∼42%) due to a high nitrogencontent in air
On the vortex identification within a linear blade cascade - an experimental research
Get PDFThis paper deals with the identification of the individual vortical structures within a linear blade cascade based on H criteria. The experimental data obtained from the pressure measurement at the cascade outlet were evaluated by a standard procedure to obtain the velocity field in one plane. Then, the vorticity in the flow field was evaluated based on Crocco’s theorem, and in the final step, the helicity density was calculated. The impact of the inlet flow angle on the velocity field as well as on the vortical structures was investigated. The effect of the value of the H threshold on the vortex identification is discussed in the last part of the paper
Municipal waste management performance: a focus on Slovakia and its LAU-1 districts
Get PDFIn this paper, we analyse the changes made to the basic EU directive on waste and assess its impact on the waste legislation of EU members. We then examine the Slovak waste strategies/programs that have implemented the EU directive on waste, namely the Waste Prevention Program, the Waste Management Program, and the Envirostrategy 2030. Based on EU waste legislation, the Environmental Strategy 2030 sets the waste treatment aims for Slovakia until 2030. However, it is questionable whether Slovakia will achieve the set goals. Our research indicates that as of 2021, Slovakia’s rate of waste incineration with energy recovery and landfilling rate of municipal waste are below the EU average, while the recycling rate, both for materials and composting and digestion, is higher. In our quantitative analysis, we examine the progress of waste management performance in Slovakia from 2017 to 2021, focusing on the LAU-1 districts. We estimate composite efficiency indicators using the techniques of Data Envelopment Analysis and Malmquist Indices. In accordance with the hierarchy of waste treatment methods, the applied models consider desirable waste operations variables (recycling and incineration with energy recovery) and undesirable waste operation variables (landfilling). Our results reveal significant variations in efficiency across the LAU-1 districts. The average technical efficiency of the 72 districts has improved from 0.714 in 2017 to 0.852 in 2021, indicating that the performance of districts is generally improving and catching up with the best-performing districts. The total performance, as measured by the Malmquist index, has improved by 45.5 %. Districts with access to waste incineration facilities with energy recovery have exhibited higher efficiency scores, benefitting from this advantage
Modern Concrete and Composites 2023
No full textThe 2nd International conference Modern Concrete and Composites 2023 is a conference held by Faculty of Civil Engineering in Prague. The conference is focused on the sharing knowledge of modern technologies, materials, investigation techniques and approaches applicable in the concrete industry and composite design.
The conference key topics were following:
new binders,
advanced technologies,
non-cementitious composites,
measurement techniques,
admixtures and additives,
recycling,
concrete under severe condition,
unique structures.
Date: October 11 - 13, 2023Venue: Hotel SKI, Nové Město na Moravě, Czech Republic
Organised by: Faculty of Civil Engineering, Czech Technical University in Prague
Guest editors:Pavel ReitermanTomáš DavidVendula Davidová
Scientific committee:Jiří MácaLenka BodnárováPetr HuňkaTomáš KlečkaKarel KolářJiří LitošPavel ReitermanJan Vodička
Local organizing committee:Pavel ReitermanPetr HuňkaBohuslav SlánskýMiroslav BroučekVendula DavidováTomáš DavidDalibor KocábMartin LuňáčekMartin VyšvařilTomáš Vlach
Guarantor of the peer review process:Pavel Reiterman
Guarantor of language editing:Miroslav Brouče
SEISMIC INVESTIGATION OF REINFORCED SOIL WALLS WITH GEOGRIDS
No full textThis study investigates the influence of various factors on the seismic behavior of geogrid-reinforced soil walls. The research involves modifying soil properties like friction angle, cohesion, elastic modulus, and Poisson\u27s ratio. The aim is to comprehend the consequent effects on the wall\u27s horizontal and vertical deformations, the lateral pressure applied to the wall\u27s surface, and the peak tensile force encountered by the reinforcements under seismic conditions with a maximum acceleration of 0.3g. The primary goal is to enhance the seismic performance of such walls and analogous scenarios. To attain this goal, a two-dimensional numerical analysis is performed employing the finite difference method and FLAC software while accounting for strain considerations. The analysis findings reveal that increasing cohesion at the wall\u27s height results in a nearly consistent peak tensile force on the reinforcements. However, the impact of cohesion on this force diminishes for wall heights exceeding 4 meters. Elevating the internal friction angle leads to a reduction in the peak tensile force on the reinforcements, particularly in the lower segment of the wall. Conversely, with increasing wall height, the decrease in horizontal pressure on the wall\u27s rear surface becomes less noticeable, eventually stabilizing at around 1 kilopascal in the upper half of the wall. Altering the soil\u27s elastic modulus demonstrates that once the value surpasses 35 MPa, the peak tensile force on the reinforcements remains stable, exhibiting no further alterations
APPLICATION OF L-SHAPED MAST CLIMBING WORK PLATFORM(MCWP) IN FAÇADE RENOVATION OF HIGH-RISE BUILDINGS: A CASE STUDY
No full textA typical mast climbing work platform (MCWP) is introduced in this paper as a new type of construction machinery for façade renovation of high-rise buildings. The application of the MCWP is presented based on a real facade renovation project where a combined arrangement of linear and L-shaped MCWP is adopted. The FEM model of an L-shaped MCWP is also established in this paper and the results are obtained. It is indicated from the results that the serviceability of L-shaped meets the requirements of the standard. Based on the duration and cost of a control group, the MCWP method can greatly improve construction efficiency and reduce cost compared with a suspended basket method
DUST DISTRIBUTION PATTERN AND OPTIMIZATION OF TUNNEL VENTILATION SYSTEM
Get PDFThis paper focuses on examining the effectiveness of a long-pressure and short-pumping ventilation system in a highway tunnel construction project in China. Utilizing computational fluid dynamics theory and ventilation system design principles, the study involves numerical simulations through finite element method to analyze dust distribution within the tunnel. The research investigates the effect of the distance of the duct from the working face and pumping ratio on dust concentration. The results indicate that optimal ventilation and dust removal occur when Lpressure set at 20m, Lpumping set at 3m, and pumping ratio is 0.7, resulting in an average dust concentration of 250mg/m3. These findings offer valuable insights for designing effective ventilation systems in tunnel construction projects, thereby enhancing dust control measures to ensure a safer working environment
A novel approach to nonlinear fractional volterra integral equations
Get PDFNonlinear Fractional Volterra integral equations (FVIEs) of the first kind present challenges due to their intricate nature, combining fractional calculus and integral equations. In this research paper, we introduce a novel method for solving such equations using Leibniz integral rules. Our study focuses on a thorough analysis and application of the proposed algorithm to solve fractional Volterra integral equations. By using Leibniz integral rules, we offer a fresh perspective on handling these equations, shedding light on their fundamental properties and behaviours. As a result of this study, we anticipate contributing distinctively to the broader development of analytical tools and techniques. By bridging the gap between fractional calculus and integral equations, our approach not only offers a valuable computational methodology but also paves the way for new insights into the application domains in which such equations arise
Modelling and analysis of three-dimensional chemically reacting, radiating Casson-nanofluid flow: thermophoresis and Brownian motion effects
Get PDFIn the presence of a porous material and a magnetic field, the authors of this work must evaluate the combined effects of chemical reaction and thermal radiation on a Casson-nanofluid flow in three dimensions towards a linearly stretched sheet. Using the Roseland approximation, which integrates the effect of thermal radiation into the energy equation, thermal radiation is included in this study. The governing equation with initial and boundary conditions is converted to dimensionless form by adding pertinent non-dimensional variables and parameters, and then numerically solved using the finite element method. The effects of key variables on velocity, temperature, and concentration are shown graphically, followed by tabular representations of the effect of these parameters on skin friction, Nusselt, and Sherwood numbers and an in-depth explanation. This is essential for several technological applications, such as oil heat recovery, termite welding, transpiration cooling, and drag reduction. A comparison of our numerical results with previously published data reveals a high degree of agreement between the two sets of information. This new research has implications for energy systems, biomedical engineering and aeronautics, and has significant implications for the food industry