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ANALYSIS OF RELATIONSHIPS BETWEEN HETEROGENEOUS RADIOMIC FEATURES OF THROMBUS IN ACUTE ISCHEMIC STROKE
Get PDFIschemic stroke is one of the most widely recognised cerebral pathologies. Its diagnosis starts with computed tomography (CT). However, a comprehensive understanding of the characteristics of the thrombus is necessary to establish an appropriate and less hazardous treatment. This study focusses on the analysis of thrombus heterogeneity in CT images of patients with acute ischemic stroke (AIS). The radiomic features of the thrombus were used to obtain the voxel distribution in the new feature space. It was then reduced using Principal Component Analysis (PCA) and subjected to visualisation techniques such as t-distributed Stochastic Neighbour Embedding (tSNE) and Uniform Manifold Approximation and Projection for Dimension Reduction (UMAP). By evaluating the morphological structure of the clusters created within patients, it was possible to determine the number of thrombus components. This information could help the physician predict the burden on the patient during thrombectomy, such as the number of attempts required for recanalization
DETECTION OF PHOBIAS FROM ELECTRODERMAL ACTIVITY SIGNAL
Get PDFThis article is focused on the preliminary study of detecting different types of phobias from the electrodermal activity signal. Electrodermal activity is independent of parasympathetic activity; therefore, it is an ideal indicator of phobias. An automatic algorithm was created for the detection of phobias, which evaluates the presence of a stress reaction to a stimulus in the form of an image sequence representing the given phobia. The results obtained using the proposed algorithm were confronted with the data provided by individual respondents in the questionnaire. By comparison, it was found that the proposed algorithm detected a greater number of phobias than reported by the respondents. According to the achieved results, we can state that electrodermal activity can serve as a means of objectifying the presence of phobias in individuals
A NEW HYBRID FRAMEWORK OF MACHINE LEARNING TECHNIQUE IS USED TOMODEL THE COMPRESSIVE STRENGTH OF ULTRA-HIGH-PERFORMANCE CONCRETE
Get PDFThe Ultra-High Performance Concrete (UHPC) as an efficient material in constructional projects needs to be investigated in terms of ingredients and their magnitudes to compute the compressive strength of concrete. Empirical determination of relationships between constituents can demand more energy and cost. At the same time, the intelligent systems have enabled us to appraise the compressive strength based on ingredients\u27 composition. Also, choosing eco-friendly materials in concrete as one of the widely-used items worldwide should be encouraged. This study has attempted to model the compressive strength of UHPC. Support Vector Regression (SVR), as a machine learning technique aligned with the Particle Swarm Optimization (PSO) and Henry\u27s Gas Solubility Optimization (HGSO), have been used to simulate the compressive strength of concrete calculated based on different materials used in the present article. Eight constituents were tested to generate the compressive strength values. Various metrics were used to evaluate the modeling process. In this regard, the R2 of test phase modeling for SVR-HGSO was obtained 0.960 while for SVR-PSO, 0.925. In the training stage, the correlation rate was computed 0.902 for SVR-HGSO, which is 1.7 percent higher than SVR-PSO with R2 0.887
A Pressure Based Compressible Solver for Electric Arc-plasma Simulation
Get PDFThe electric arc discharge in a liquid medium is used in several applications such as the sterilization of the liquid by UV radiation, the fracturing of rocks by shock wave, the circuit breakers in oil bath or the forming of mechanical parts. Thus, describing the physics of the arc in a liquid and in particular its interaction with a liquid interface is an important issue to better characterize this type of configuration. However, such a challenging task requires to couple high-fidelity solver for compressible two-phase flows with liquid phase change and a plasma solver to describe the plasma and its interaction with the bubble. To study this type of medium, we use a compressible formulation of the fluid equations. For this purpose, a pressure based solver has been developed for the computation of the energy conservation equation. Moreover, our numerical model uses the immersed boundary method to simulate the solid electrodes. The numerical model is briefly described in this paper and the first results of the electric arc discharge in steam water are presented. To our knowledge this pressure based model has never been used to describe plasmas and electric arc discharge
Compression behaviour and failure mechanisms of a safety culvert made of hollow high-performance concrete blocks
Get PDFThe safety culvert composed of hollow high-performance concrete blocks is designed to reduce the risk of injury in the event of a collision. This work presents a new design with an opening for water flow, tests it, identifies its weaknesses, and discusses possible improvements. The numerical model is constructed, validated by experiment, and used to study the effect of design parameters on the load capacity, compression behaviour, and failure mechanisms. The response varies most markedly with the opening diameter. The failure mode changes from bending failure to concrete crushing as the diameter decreases. The effect is most pronounced for diameters less than 400 mm, where the load capacity increases by 6 kN per millimetre reduction. If a crack develops in the culvert during its service life, the first such crack will form in the top layer of blocks, followed by a crack in the opening. These areas should be monitored more closely during follow-up tests with passing vehicles
Experimental evaluation of aluminothermic welds
Get PDFThe article presents a study of the mechanical processes occurring during the aluminothermic reaction using experimental methods (strain gauges, digital image correlation, thermography, scanning electron microscopy, profilometry). The aluminothermic reaction is a highly efficient welding method due to its exothermic behaviour, however, it places considerable demands not only on the welding technique, but also on the capabilities of the experimental methods used; these limitations are also discussed in the article. The aluminothermic reaction is associated with the formation of a localised heat source with a time evolution dictated by the technological procedure, which manifests itself in heat propagation to the surrounding weld material. The unequal evolution of the temperature field is the fundamental cause of the appearance of the heat affected zone or local deformations or surface curvature, which was the focus of the experimental methods deployed above and the results of which are shown in the article
18th Youth Symposium on Experimental Solid Mechanics
No full textThe 18th Youth Symposium on Experimental Solid Mechanics was held in Telč, in June 11 - 14, 2023.
The 18th symposium continues both the long tradition of this conference series and introduces novel elements under auspices of IMEKO TC15. The YSESM 2023 symposium provides a forum for young researchers and engineers, students and PhD students dealing with subjects of experimental mechanics. In addition, the combination of the experimental mechanics with modern numerical methods will be a new focus of this 18th Symposium.
The conference key topics were following:
Conventional and Advanced Experimental Methods in Solid and Fluid Mechanics
Non-Destructive Testing and Inspection
Measurements in Material Science
Computer Assisted Testing and Simulation
Engineering Design Simulation
Hybrid Methods, Experimental Techniques – Numerical Simulation
Optical Methods and Image Processing
Measurements in Biomechanics
Sensor Techniques for Micro- and Nano-Applications
Measurement Methods for Forensic Engineering
Scientific comittee:Lajos Borbás - Budapest University of Technology and EconomicsTomáš Doktor - Czech Technical University in PragueMarta Peña Fernández - Heriot-Watt UniversityDaniel Kytýř (chair) - Institute of Theoretical and Applied Mechanics,CASZoltán Major - Johannes Kepler University LinzGiangiacomo Minak - University of BolognaNejc Novak - University of MariborSascha Senck - Upper Austria University of Applied Sciences WelsJacek Tarasiuk - AGH University of Science and Technology in KrakówMatej Vesenjak - University of MariborPetr Zlámal - Institute of Theoretical and Applied Mechanics, CAS
Local organizing comittee:Tomáš DoktorVeronika DrechslerováJan FaltaDaniel KytýřJan ŠleichrtPetr ZlámalBlanka Žaloudková
Guarantor of the peer review process:Daniel Kytýř
Guarantor of the language editing:Dalila El Oumal
Complementary Experimental and Simulation-based Characterization of Transient Arcs
Get PDFElectric arcs generated by transient lightning-type surge currents in protection devices for low voltage appliances are studied by optical emission spectroscopy and spectra simulations. A surge pulse amplitude of 5kA and 8/20µs shape are applied. The arc radiation is recorded by a 3/4m spectrometer and a high-speed camera equipped with metal interference filters for the O I (777nm) and Hα (656nm) lines. Absolute calibration was realized using a tungsten strip lamp. The arc images indicate a non-symmetrical shape. To determine the plasma properties, accompanying simulation solving the equation of radiative transfer for a given pressure and a temperature profile was carried out assuming local thermodynamic equilibrium. Line broadening due to the Stark effect is taken into account. The computed and measured spectra are compared. The conditions are varied until the measured and computed spectra match
Impact of Ablation Based Self Blast Nozzles on Load Break Switch Current Interruption Performance
Get PDFIn this contribution, SF6 free ablation assisted medium voltage load break switchgear, has been investigated. In these switches, gases generated by the arc polymer interactions are trapped in expansion chambers and are released back onto the arc at the current zero crossing. This increases the current interruption capability of the switch without the use of additional mechanical parts, as opposed to using a puffer to blow on the arc. Existing self-blast research, in medium voltage load break switchgear, has focused on blowing axially or tangentially onto the arc in a cylindrical arcing channel. More geometries are possible. In this paper, alternative self-blast blow-position and the presence of obstructions in the arcing channel have been investigated experimentally and with cold flow simulation. It has been determined that blowing right onto the arc centre is not optimal for cooling the arc, and that the presence of an obstruction in the arc channel is beneficial to arc interruptions
EXPERIMENTAL INVESTIGATION OF PERVIOUS CONCRETE TO IMPEL IT IN THE INFRASTRUCTURE OF PAKISTAN
No full textPakistan is facing adverse environmental issues peculiarly in major cities. The condition gets worst during monsoon period when the whole city faces the urban flooding due to stagnation of storm water on all major streets and areas. The main reason is the lack of infra-structure to mitigate the crisis which is faced by the country during whole rainfall season. The introduction of Pervious Concrete in major pavement infra-structure can easily limit the problems of sump of rain water. As a part of road infrastructure, the upper layer of pavement can be pervious, making runoff water to move to sub-base. This paper offers the exploratory research to ascertain the compressive strengths and infiltration rate of different samples of Porous Concrete following the American Concrete Institute guidelines. The experiments were done with varying the properties of Pervious Concrete. The effects which were considered are curing time, mix proportion, percentage quantity of fine aggregate, ratio of water to cement and varying coarse aggregate size. The mix design ratio considered were 1:4, 1:5 and 1:6. For further experiment of infiltration rate, the custom slab was formed with dimensions 2’x1’x4” and was tested for all the desired ratios. For the purpose of cost comparison, a fixed size on land is kept as standard. The cost is compared for construction on the land, using three different materials: Pervious concrete, Traditional concrete and Asphalt premix.It was showed that the Traditional concrete is cheaper than the Pervious and Asphalt layer but Pervious concrete is also economical than Asphalt layer