CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
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The effect of the external magnetic field on the power of the laser passing through the magnetized plasma and the calculation of the radius of convergence and the investigation of the condition of the beam\u27s filamentation in the Medium
Get PDFIn this article, the power of a laser passing through a magnetized plasma medium which is affected by an external magnetic field is calculated.The change in the intensity of the magnetic field and its rotation around the axis of laser beam propagation in the plasma, on the power of the passing beam is investigated.This work is done based on the indirect effect of the magnetic field on the density distribution of electrons in the plasma, which we can consider the density changes as changes in the refractive index of the medium, so the laser power in this case is different from the case where there is no magnetic field. Also, the condition of beam filamentation has been researched as one of the third-order nonlinear phenomena, and the convergence radius has been calculated under these conditions
Optimised rotating energy-efficient clustering for wireless sensor devices by sewing training-based optimisation
Get PDFWireless sensor networks (WSNs) have become well-known as innovative, active, and robust technology accepted in many real-world applications. Due to the power supply restrictions and the power limitations of sensors that are typically known in WSN, using energy becomes a challenge in networks. These two restrictions are essential for achieving energy efficiency and raising the network’s lifetime in WSN. Clustering develops multipath routing and scalability, performing optimisation, and making WSN naturally more reliable. This paper introduces an Optimised Rotating Energy Efficient Clustering for Heterogeneous Devices (OREECHD). OREECHD is a clustering technique for heterogeneous WSNs that presents a unique cluster head selection method based on node residual energy and node-induced work. OREECHD defines the term intra-traffic rate limit (ITRL). The document outlines communication restrictions for traffic inside a network with WSNs. ITRL could be applied to develop energy efficiency. We apply the Sewing Training-Based Optimization (STBO) algorithm to recognise the best ITRL in various WSN adjustments. The simulation results show that the proposed algorithm using clustering based on the best ITRL improves the energy consumption in the sensor network by 8.9 % over the REECHD. The simulation outcomes account for the number of dead nodes present in the OREECHD and REECHD networks during the 1 400 and 1 250 rounds, respectively. The network lifetime is significantly improved compared to REECHD, since OREECHD is a classic example of an unequal clustering algorithm. The network’s lifetime is 1 200 rounds, which exceeds the REECHD lifetime of 800 rounds. The rate of residual energy at the average node decreases from 19.39 % to 15.41 %
Tunisian engineers: protagonists of Tunisia’s modernisation. Two key moments: 1956 and 1987
Get PDFEngineers have played a key role in Tunisia’s modernisation process during and after its independence. They were crucial in almost all aspects of life. From the beginning of the reformist project, they were close to power and even made demands according to their interests. However, they did not know how to generate such cohesion within their group that would allow them to consolidate and have political influence. Two fundamental moments in the process of modernisation showing the evolution of a profession that went from the height of its splendour to its decline, with all that this meant and implied for all aspects of Tunisian life
The decimalisation of Republican time. The French Revolution which failed (1793–1795)
Get PDFThe French Revolution is rightly regarded as a major milestone in human history. Its most famous ideas of equality and freedom have endured up to the present day, but these were not the only ideas promoted during this turbulent time. In order to establish a new social order, the revolutionaries proposed, among other things, the use of decimal time which was part of the so-called Republican calendar. This chapter will focus on the circumstances of the creation, application, and the use of the decimal (time) system, analyse the reaction of society, and explain the reasons for the early demise of this revolutionary undertaking
Development of hydration temperatures on cement pastes
Get PDFThis article deals with the possible combination of high temperature fly ash with fluidised bed fly ash. The main objective of the experiment is to verify the effect of the combination of these two energy by-products on simpler systems – cement pastes. In the experimental part, the evolution of hydration temperatures and the time course of volume changes were monitored. The results obtained indicate that the addition of fluid fly ash to the mixture intensifies the hydration reaction, despite the increase in the value of the water to cement ratio of the mixture. At the same time, there is a slight increase in volume changes, which can be considered as a very valuable contribution to technical practice, taking into account possible ecological or economic aspects
Mechanical properties of cement pastes containing plasma-treated silicon-based materials
Get PDFThe study delves into the impact of waste silicon-based materials on the mechanical characteristics of the resulting cement pastes. The investigation uses Portland cement CEM I 42.5R in conjunction with silicon-based waste materials sourced from the packaging industry, specifically from Recifa, a.s. Variations between the sample groups arise from differences in the concentration of silicon-based materials and the method of surface treatment. The inquiry seeks to assess the effects of two distinct levels of Si-based material incorporation, namely 10 wt. % and 20 wt. %, along with plasma treatment involving two different gases: oxygen (O2) and hydrogen (H2). The mechanical attributes under scrutiny encompass compressive and flexural strengths. The evaluation of mechanical properties is carried out on samples aged 28 days, with dimensions measuring 20 × 20 × 100 mm
Production of concrete pavements using mixed cements
Get PDFThis paper discusses the possibility of assessing the k-value of power plant fly ash using durability. Compressive strengths, activity indices, pressure water seepage depth and carbonation depth were determined for cement mortars with 10, 20 and 30 % cement replacement by fly ash for ages of 7, 28 and 60 days. The k-values for each cement substitute were determined for each age using the relationship between water/cement ratio and compressive strength. Using the results of the depth of pressurized water seepage and depth of carbonation, the determined k-values were assessed and k-values that are safe for use of power plant fly ash in aggressive XC and XD environments were determined
Tomographic and mechanical study of 3D printed porous polymer structure under compression
Get PDFThis study investigates the influence of open porosity rate and trabeculae diameter on the compressive behavior of structure printed by DLP technology. Three types of structures have been studied : two periodic structures (Cubic and Octet) and one aperiodic structure (Voronoi-based). Each of these structures are printed with a porosity of 40, 60 and 80 % and also with two different trabeculae diameters: 0.45 mm and 0.66 mm. We investigated porosity by micro-tomograpy with ImageJ for the data treatment. We determined the curing time by making a compressive test for different lengths of UV cure. The first results of the study show that Cubic structure has better Young’s Modulus and also better mechanical stress than Octet and Voronoi-based structures
Characterization of woven composite material under multiaxial loading regimes using FE-based stereocorrelation
Get PDFIn this paper, woven glass fiber composite samples were subjected to three different cyclic loading histories (i.e., tensile, shear and combined loading at 45° via the Modified Arcan Fixture. During the experiments, the samples were monitored by a stereovision system. Finite Element based stereocorrelation was used to measure the displacement and strain fields. The analysis of the experiments revealed different damage mechanisms. Furthermore, for the 45° experiment, the highest strain levels were reached, whereas for the tensile test, the highest stress levels were achieved
BIM CONTROL METHOD FOR HIDDEN QUALITY COST OF PREFABRICATED BUILDING CONSTRUCTION PROJECT
Get PDFAt present, the hidden quality cost in the construction process of prefabricated building projects in China is too high. If it is not controlled, there will inevitably be a "benefit funnel". Based on the construction of cost BIM control model, the information integration platform of prefabricated construction project is designed. Utilizing the details provided regarding the model and platform, the technique of constrained machine learning is employed for managing the concealed expenses related to quality in prefabricated construction ventures. By optimizing cost control, the ultimate objective of managing expenses is achieved. The outcomes of experiments illustrate that this approach has the capability to proficiently govern the covert quality expenses linked with prefabricated construction projects. It significantly enhances the focused and efficient management of comprehensive and evolving oversight of quality-related expenses throughout the construction process