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Optical Emission Spectroscopy of Cadmium Dominated Discharges Applied for Assessment of Explosion Protection
Get PDFAn assessment for the safe use of electrical equipment in explosive atmospheres can be performed with the aid of a spark test apparatus. Therefore, an anodic tungsten wire with 200 µm diameter is moved along the surface of a rotating cadmium disc (cathode). The explosion chamber enclosing the electrodes is filled with a highly explosive mixture of hydrogen and air. Depending on surface topology and relative movement of the contact pair, discharges occur randomly. A model contact device is used to investigate the plasma properties and the discharge characteristics near the thermo-chemical ignition threshold of the explosive atmosphere that typically occur at voltages around 30V and currents around 30mA.Spectroscopic investigations reveal that the emission of the discharges is dominated by atomic lines of cadmium, which allow the determination of distribution temperatures
Statistical Methods for Identifying Small Differences in the Thermal Interruption Performance of SF6 Alternatives
Get PDFThis contribution will present thermal current interruption measurements performed in pure CO2 with a puffer circuit-breaker test device and establish a statistical method to assess the reignition probability as a function of the prospective current slope. Its efficacy will be demonstrated with measurements of the interruption limit scaling with respect to the pressure buildup inside the test device. A separate contribution will apply these methods to evaluate the influence of fluorinated additives on the switching performance
HISTORICAL RETAINING WALLS MONITORING: A CASE STUDY OF DEBOSQUETTE WALL OF KYIV-PECHERSK LAVRA
Get PDFGeospatial monitoring of historic buildings has a valuable meaning for their restoration and preservation measures. The preparation and accomplishment of such monitoring have their features and cannot be standardized. Therefore, in each particular case, monitoring is carried out for specific requirements and conditions. The paper presents the results of geospatial monitoring for a part of the UNESCO object Kyiv-Pechersk Lavra. The primary subject of geospatial monitoring is a retaining wall known as the Debosquette Wall. The wall was built in the XVIII century and underwent restoration in 2014. A geospatial monitoring system has been established to prevent undesirable damage and displacements. Assigning the necessary observation accuracy for such a complex object is difficult. In the paper, the modern approach to observation accuracy calculation has been suggested and studied. The approach is based on the application of structural mechanics principles. The structural analysis of the Debosquette Wall has been accomplished. The output of the analysis was applied to calculate the required observation accuracy. The geospatial network and monitoring scheme were developed based on the calculated accuracy. The monitoring proceeded for half a year in 2012-2013, was interrupted for one year, and kept on in 2015. The primary stress was made on the horizontal displacements in that these displacements are the primary threats to the wall stability. The in-depth analysis of the monitoring results has been accomplished. It was found that the displacements have stayed within the allowable values. The developed monitoring approach is recommended for similar projects
Stereolithography for manufacturing of advanced porous solids
Get PDFThe aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high absorption of impact energy. SLA is an additive manufacturing technology employing the principle of liquid resins curing moderated by radiation of a wavelength from ultra-violet band where resulting material parameters are tunable by setting of the curing process. The batches of samples manufactured using three different resins were subjected to quasi-static uni-axial tensile and compression tests. Acquired data were processed to derive deformation behaviour expressed as stress-strain diagrams and fundamental material properties. Based on the knowledge obtained from the mechanical tests, the setup of the fabrication parameters, the most suitable resin for manufacturing of the lattice structures and the overall suitability of SLA technology for the fabrication of advanced porous materials, were determined
Vision Zero application on Czech railways
Get PDFThe railway is perceived as a modern, safe and environmentally sustainable way of transporting people and goods. In the past, appropriate innovations in the field of infrastructure and vehicles, combined with an attractive operational concept, have gradually become the backbone of public transport in the country. Even in this system, similar to other transport systems, there are accidents (events of emergency) or potentially risky situations. The paper places the issue of railway safety in the legislative context and uncovers the points of view from which the safety of railway traffic can be viewed
Possibilities of using commercial electronics to measure driver physiological functions in a vehicle simulator
Get PDFThe aim of this paper is to explore the potential of using inexpensive, commercial electronics such as a smartwatch or chest belt to measure human physiological functions while driving in vehicle simulator, both to improve safety and to use these devices in other experiments to facilitate their conduct and replace more complex laboratory equipment. In the first part of the paper, the signs of stress and cognitive load through physiological functions are researched, then the possibilities of measuring these signs are explored. This is followed by an experiment in which two commonly available devices are compared in terms of accuracy and usefulness for measurement during the experiment
AI-assisted study of auxetic structures
Get PDFIn this study, the viability of using machine learning models to predict stress-strain curves of auxetic structures based on geometry-describing parameters is explored. Given the computational cost and time associated with generating these curves through numerical simulations, a machine learning-based approach promises a more efficient alternative. A range of machine learning models, including Artificial Neural Networks, k-Nearest Neighbors Regression, Support Vector Regression, and XGBoost, is implemented and compared regarding the aptitude to predict stress-strain curves under quasi-static compressive loading. Training data is generated using validated finite element simulations. The performance of these models is rigorously tested on data not seen during training. The Feed-Forward Artificial Neural Network emerged as the most proficient model, achieving a Mean Absolute Percentage Error of 0.367 ± 0.230
Validation Approach for a Spatially and Temporally Resolved Fault Arc Model
Get PDFThis paper presents a method to validate arc models for fault arc applications by examining the effect of changed boundary conditions on arc parameters, e.g. voltage and pressure build-up. The study shows the impact of ignition location on arc voltage and pressure build-up and prediction accuracy of the presented model. The results indicate insufficient accuracy in predicting arc voltage during dynamic phases, while the pressure build-up prediction aligns well with the experimental results
REDUCTION OF INDOOR RADON CONCENTRATION IN A ROOM USING HEAT RECOVERY VENTILATION
Get PDFIncreased requirements for the energy efficiency of buildings often lead to an increase in the tightness of the building envelope. A lower level of ventilation subsequently worsens the quality of the indoor air and also causes an increase in the indoor radon concentration. This problem can be solved by using ventilation devices with heat recovery. The paper deals with the influence of local ventilation equipment with heat recovery on indoor radon concentration. The aim of the paper is to evaluate the rate of reduction of indoor radon concentration by using this method of ventilation
An exploratory gallery for Luka tunnel on the D3 motorway
Get PDFThe Luka tunnel is designed for the 0302 Jílové – Hostěradice section of the D3 motorway. This has a length of 1843m and will consist of two tunnel tubes of T 9.5/100 category. It is proposed that a 1354m long exploratory gallery be put in place in the left-hand tunnel tube. It will be used for detailed geotechnical exploration in a rock environment that has been negatively affected by past mining activities. The exploratory gallery will be constructed using a procedure that will limit the possible stability risks during its excavation. The knowledge gained from the excavation of the gallery and from the comprehensive survey operations undertaken will serve as the essential basis for the reliable design and safe construction of the tunnel tubes. The current state of the D3 motorway differs greatly along its individual sections. The more southerly located sections D 305/II (Nová Hospoda) to D 309 (Úsilné) are in operation. Section D 310 Úsilné – Hodějovice with the České Budějovice bypass is under construction, and the construction in the direction of Austria has not yet proceeded [1]. The situation is very disappointing particularly in the Central Bohemian region, even though exploration operations are underway to a limited extent in sections D 301 to D 305/I, as construction has not yet started due to problems with obstructions or objections by activists of various types. The problem is that it is demonstrable that the existing road I/3, which is also part of the main international road route E55, is already completely inadequate both in terms of capacity and in terms of its alignment running through several developed residential complexes. After the completion of the D3 motorway, this road will be usable as an alternative diversion route without major modifications in the event of a required closure of the motorway