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Integrated cyclic timetable on the railways in the Karlovy Vary region
Get PDFThe concept of public transport with periodic timetables has been slowly spreading in the Czech Republic for many years. Together with the announcement of tenders for the operation of compulsory transport according to the European Parliament’s Regulations 1370/2007 and 2338/2016, circular integrations occur in many regions, which usually represent the adjustment of public transport to a concept corresponding to current trends and needs
50th Conference Foundation Engineering Brno 2022
No full text50th CONFERENCE FOUNDATION ENGINEERING BRNO 2022
The traditional yearly conference of Foundation Engineering Brno is organized by the Czech Geotechnical Society. This is the largest annual event in the field, where researches, academicians, designers, investors and contractors present, share and discuss the results of their research and share their experiences with each other.
Each year is focused on a certain topical subject. Selected experts from abroad are invited for Keynote lecture for each conference. This issue of Acta Polytechnica Proceedings includes selected scientific papers that were presented at the 50th Conference of the Foundation Engineering held in Brno in 2022. Key Topics: Geotechnical engineering around us after fifty years.
Date: November 14 - 15, 2022Venue: BrnoURL: www.cgts.cz
Organized by: Czech Geotechnical Society of the Czech Institution of Civil Engineers
Guest editor: Daniel Jirásko
Scientific comittee: Jana Frankovská (STU Bratislava, Slovak Republic)Eva Hrubešová (TU Ostrava, Czech Republic)Věra Glisníková (VUT Brno, Czech Republic)Lubomír Klímek (GEOtest, Czech Republic)Jan Masopust (Czech Technical University in Prague, Czech Republic)Lumír Miča (VUT Brno, Czech Republic)Petr Nosek (Foundation Engineering company, Czech Republic)Jindřich Řičica (EFFC, UK)Ivan Slávik (STU Bratislava, Slovak Republic)Petr Svoboda (VUT Brno, Czech Republic)Peter Turček (STU Bratislava, Slovak Republic)
Local organizing comittee: Ivan VaníčekDaniel JiráskoJiří BartákTaťana HoloušováJan PruškaMichael Remeš
Guarantor of the peer review proces:Daniel Jirásko
Guarantor of language editing:Renáta Nivenov
DESIGN AND TESTING OF A DEVICE FOR HUMAN LIMB MULTIFREQUENCY COMPARATIVE BIOIMPEDANCE MEASUREMENT– PRELIMINARY STUDY
Get PDFBioimpedance is the ability of biological tissues to impede the flow of electrical current. It is often measured as a means of detecting volume and structural changes in various biological tissues. The purpose of this work was to design a two-channel portable device for measuring multifrequency bioimpedance of human limbs. The device was constructed specifically for evaluation of the bioimpedance measurement as a possible tool for aiding in diagnosis of soft-tissue structural changes in the muscles of human limbs by continuously comparing bioimpedance of one limb to the other. The proposed device is based on impedance converter AD5933. It is designed for noninvasive measurements on the human body with low amplitude alternating current at frequencies between 1 kHz and 100 kHz. The device was tested for electromagnetic compatibility, accuracy and used in laboratory measurements for detection of muscle edema on a bioimpedance model. It is capable of measuring impedance up to 100 kΩ with a relative measurement error below 1.84%
SIMULATION OF PREMATURE VENTRICULAR CONTRACTIONS IN PATIENT SPECIFIC BIDOMAIN VENTRICULAR MODEL
Get PDFThe goal of the study was to simulate electrical activation of the heart ventricles and corresponding body surface potentials (BSPs) during premature ventricular contractions (PVC) using the patient specific realistic homogeneous model of cardiac ventricles and the torso. Real position of the initial ectopic activation during PVC was determined by intracardial measurement in the upper part of the right ventricle near the His bundle and confirmed by successful catheter ablation of the PVC origin. Simulated electrical activation in the ventricular model was started at the position of the initial ectopic activation as well as at several other sites at various distances from this position. The propagation of electrical activation in the ventricular model was modeled using bidomain reaction-diffusion (RD) equations with the ionic transmembrane current density defined by the modified FitzHugh-Nagumo (FHN) equations. The torso was modeled as a homogeneous passive volume conductor. The RD equations were numerically solved in the Comsol Multiphysics environment. Simulated ECG signals and BSPs were compared with those measured during PVC in a real patient. The polarity and shape of simulated and measured ECG leads as well as the BSP distribution during the PVC were in best agreement when the stimulated region was less than 10 mm from the position of the initial ectopic activation
Derivation of entropy production in a fluid flow in a general curvilinear coordinate system
Get PDFThe paper deals with the derivation of the entropy production in the fluid flow performed in a general curvilinear coordinate system. The derivation of the entropy production is based on the thermodynamics laws as well as on the balances of mass, momentum, and energy. A brief description of the differential geometry used in general curvilinear coordinates is presented here as well to define the used notation.The application of this approach is then shown in the evaluation of the entropy production along the suction side of the blade, where the calculation was performed using available experimental data
Research on a safety evaluation system for railway-tunnel structures by fuzzy comprehensive evaluation theory
Get PDFLong-term health detection of railway-tunnel is the development direction and trend of future railway tunnel research. Based on the actual engineering of a railway tunnel, this study developed a safety evaluation model for railway tunnel structures using a fuzzy comprehensive evaluation method and examined a health state evaluation method suitable for most railway tunnel structures. The results showed that the evaluation method comprehensively reflected the impact of various factors, which had strong practicality. The evaluation results were clear, accurate, and consistent with engineering practice. When using the safety factor index to study the stress of a railway tunnel structure, Midas/civil analysis showed that different levels of the surrounding rock structural vault in railway tunnels were in a tensile, control-bearing capacity state. When calculating safety factors, the range of a 60° central angle of a railway tunnel vault was calculated according to the tensile control-bearing capacity. Theoretical formulas of the range of the center angle φ0 of the vault tension zone were derived and then verified by experiments and numerical analysis
A comparative experimental investigation of high-temperature effect on fibre concrete and high strength concrete using UT and CM methods
Get PDFIn this paper, a 28-day compressive strength test has been performed on samples including normal fibre concrete and high-strength concrete. The ultrasonic test (UT) as a non-destructive and compression machine (CM) as a destructive test were applied, and the results were compared. To investigate the effect of temperature, the samples were subjected to 200, 400, 600, 800, 1000, and 1200 degrees Celsius and the exposure time was equal to 30, 45, 60, 90, 120, and 180 minutes. Based on the results, it was observed that the minimum error observed between the UT and CM tests was 2.9 % and the maximum error between the two methods was 10.9 %, which shows the high accuracy of the ultrasonic testing method in determining the specimen’s strength. The average probable error of the method is determined to be around 6.8 %.Based on the results of the average decrease in compressive strength versus the heat exposure time, it is observed that the trend of changes and decrease in resistance over time for both types of tests is almost the same and has a negligible difference. At the end of 180 minutes of exposure, the resistance ratio for the ultrasonic test is 69.8 %, and 71.1 % for the compression machine. Furthermore, according to the average reduction in compressive strength due to heat exposure time, it has been observed that the results of the UT and UM tests have slight numerical differences, however, the trend of changes and reduction in resistance over time for both types of tests is almost the same. Finally, the accuracy of the UT in determining the compressive strength of specimens at high temperatures is fully confirmed
Fractional multi-loop active disturbance rejection control for a lower knee exoskeleton system
Get PDFRehabilitation Exoskeleton is becoming more and more important in physiotherapists’ routine work. To improve the treatment performance, such as reducing the recovery period and/or monitoring and reacting to unpredictable situations, the rehabilitation manipulators need to help the patients in various physical trainings. A special case of the active disturbance rejection control (ADRC) is applied to govern a proper realisation of basic limb rehabilitation trainings. The experimental study is performed on a model of a flexible joint manipulator, whose behaviour resembles a real exoskeleton rehabilitation device (a one-degree-of-freedom, rigid-link, flexible-joint manipulator). The fractional (FADRC) is an unconventional model-independent approach, acknowledged as an effective controller in the existence of total plant uncertainties, and these uncertainties are inclusive of the total disturbances and unknown dynamics of the plant. In this work, three FADRC schemes are used, the first one using a fractional state observer (FSO), or FADRC1, second one using a fractional proportional-derivative controller (FPD), or FADRC2, and the third one a Multi-loop fractional in PD-loop controller and the observer-loop (Feedforward and Feedback), or FADRC3. The simulated Exoskeleton system is subjected to a noise disturbance and the FADRC3 shows the effectiveness to compensate all these effects and satisfies the desired position when compared with FADRC1 and FADRC2. The design and simulation were carried out in MATLAB/Simulink
Measurement and evaluation of cement paste porosity by electrochemical impedance spectroscopy
Get PDFPorosity is an important part of cement paste microstructure, which significantly influences the mechanical properties (especially durability and strength) of cement-based materials. Electrochemical impedance spectroscopy (EIS) is a non-destructive method used to measure the pore system utilizing a range of frequencies of electric current, which is fed to the cement paste by stainless steel electrodes. The pore volume is obtained from the pore resistance and the matrix capacitance measured by EIS. This paper deals with the evaluation of porosity based on resistance values from EIS on a sample of pure CEM I 42.5R Portland cement paste at 3 different hydration times (age 7, 14, 28 days)
Experimental analysis of the railway truss bridge using modern methods
Get PDFExperimental analyses of civil engineering structures have been carried out for decades. While in the past, mainly static load tests of new structures were performed, a few severe accidents with fatal results caused a lot of emphasis to be given to monitoring existing structures recently. The need for continuous or periodical evaluation of static or dynamic behaviour of structures in operation led to a good progress in the development of modern methods for experimental analysis. The paper deals with one of the modern methods of experimental analysis – the DIC method. Possible application of the DIC method was verified by an experimental analysis of a railway truss bridge in Rataje nad Sázavou. The experiment was divided into two stages. During the experiment, deflections of the bridge measured by LVDT sensors and the DIC method were compared. Technological problems of the DIC method were found in the first stage. One of the problems was related to stability of the camera tripod. A solution was proposed and verified during the second stage