CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
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Collapse potential and ultrasonic pulse velocity of loess soils after treatment with expanded perlite and metakaolin
Get PDFCollapsible soils, including loess, can support heavy loads at their natural humidity but then collapse rapidly and lose a substantial volume when the humidity increases. Soil collapse potential at different immersion stresses was investigated according to ASTM D5333. Different immersion stresses, including 100, 200, 300, 400, and 500 kPa, were used to evaluate the stress-strain behavior of soils before and after saturation. The results indicated that soil collapse potential rose with a raising of immersion stress, resulting in the highest soil collapse potential at 500 kPa immersion stress. Furthermore, the effectiveness of expanded perlite and metakaolin in treating loess soils was examined. The results revealed that the soil collapse potential reduced with an increase in perlite and metakaolin up to 8 %. Also, perlite had a more significant impact on the soil collapse potential than metakaolin. The interlocking force between soil particles was enhanced as the perlite quantity rose, and perlite prohibited soil particles from slipping on each other. Metakaolin decreased the soil collapsibility due to the pozzolanic and chemical reactions which increased particle bonding. The ultrasonic pulse velocity of soils decreased as the percentage of perlite increased. Because the perlite was not spread homogeneously, and the waves can be stuck in the heterogeneities, Metakaolin acted as a filler and increased the ultrasonic pulse velocity of the soils
INFRARED THERMOGRAPHY - COMPARISON OF INNER CANTHUS OF THE EYES AND FOREHEAD SURFACE TEMPERATURES IN HEALTHY ADULTS
Get PDFInfrared thermography (IRT) is a non-invasive method for surface temperature measuring. The use of the contactless IRT method is comfortable for the patient, fast and hygienic. However, this method does not provide information about the core body temperature because the temperature is measured indirectly from the surface of the human body. There are several places on a human body from which surface temperature is commonly measured; the methods of measurement and application of the device is inconsistent. The aim of this article is to show the difference between the temperature measured on the forehead and on the inner corner of the eye in healthy persons, with reference to the recommendations of ISO standard. This is mainly due to the fact that compliance with the ISO standard is not always met, as shown by the personal experience of the authors. The body surface temperature was measured by use infrared camera WIC 640 under control of calibrated model of a black body. The data from 59 different volunteer subjects show statistically significant difference in measured temperature from both selected positions. The obtained median temperature values were 35.04 °C from forehead area and 35.85 °C from canthus of eyes. The observed difference was more than three-quarters of a degree Celsius for the median value. The maximum observed temperature difference within the observed group was almost 1.94 °C. The present study defines surface temperature from canthus of eye and undoubtedly shows how important it is to comply with the standards and recommendations of professional thermology societies
Remapping and simulation of EFI system for SI engine using piggyback ECU
Get PDFElectronic fuel injection (EFI) is a complex system, many parts are connected together from mechanical parts to electronic parts to control the internal combustion engine. It must ensure many different works and the most important thing in motorsport to achieve is power optimization. High power and engine responsiveness are often desired to gain a competitive edge. Usually motorsport enthusiast will upgrade the car standard with aftermarket components such as higher rating turbo, longer duration camshafts and exhaust system. These are difficult to approach, time-consuming and expensive tasks compared to the ECU calibration method. And in Vietnam, most customers who want to change vehicle performance are based on the Remap method on Factory ECU. By using vehicle performance regulation method with piggy-back ECU, it is easier for the user to adjust than the popular Remap method. With advantages such as low cost and easy installation. And currently there are very few documents describing and evaluating the effectiveness of piggy-back ECU installed in vehicles. So in this paper, experimentally to reconstruct the electronic fuel injection system with piggy-back ECU was performed, then simulated the control algorithms of the electronic fuel injection system on LabVIEW and compared the results with the experiment, based on the simulation model of the operation algorithm of the EFI system with many cases in different load engines and engine speeds. Simulation results are used to evaluate the algorithm on the piggy-back ECU
FIELD EXPERIMENTAL STUDY ON EXTERNAL PRESTRESSING REINFORCEMENT OF A 420M PC CONTINUOUS BEAM BRIDGE
Get PDFIn this paper, the practical engineering of a 420 m PC continuous beam bridge is taken as the research object, and an external prestressing reinforcement method is proposed to reinforce the damaged and cracked girder. The paper is to study the structural performance of PC continuous beam bridge before and after reinforcement. The heavy vehicle loading test of reinforced PC continuous beam bridge was carried out. A total of three test spans were selected, and each test span selected seven deflection test section and a strain test section. The corresponding finite element model was established and verified by the test results. Finally, it was concluded in this study that the external prestressing reinforcement method has a good effect on improving the loading capacity and overall performance of damaged bridges
Possible approaches for processing of spherical images using SfM
Get PDFSpherical cameras are being used more frequently in surveying because of their low cost and possibility to process spherical images with conventional SfM methods. Fish-eye lenses are now frequently found on modern 360° cameras, allowing for the capture of the entire scene and subsequent model reconstitution by a non-photogrammetrist specialist. Gyrospherics are a feature of cameras that ensure image stabilization to reduce blur when the camera is moving. This feature allows it to capture moving scenes in time-lapse mode. However, two main factors - hardware parameters and software algorithms - affect the quality of the images that are captured. The 360° camera design allows for a variety of data processing methods by SfM. These images were created using multiple image sensors and lenses from each 360° camera. These images can be processed individually or by applying rules to define relationships between images. Also, images from cameras can be stitched and processed with a spherical camera model. In this paper is proposed processing methods of data from 360° cameras and estimated accuracy of each method
EVALUATION OF DIMENSIONAL ACCURACY AND DENSITY OF DENTAL STRUCTURES MANUFACTURED BY DIFFERENT TECHNOLOGIES
Get PDFThis study focuses on the fabrication and analysis of a total of 90 dental structures (metal parts of dental prostheses – coping, bridges) of 3 types made of cobalt-chromium alloy through different fabrication technologies which include casting, additive manufacturing by selective laser melting (SLM) and subtraction technology by CNC milling. The manufacturing accuracy analysis was carried out by comparing the nominal model and the actual model obtained by 3D scanning of the fabricated dental structures in GOM Inspect software. Density measurements were performed by helium-based gas pycnometry. The data obtained were statistically analysed and a statistically significant difference was confirmed between the subtraction and additive technology. Based on the available manufacturing technologies, materials and equipment used to fabricate the samples for this study, it can be concluded that dentures fabricated by 3D printing are more accurate than dental structures fabricated by milling or casting technology
INFLUENCE OF THE ARC WELDING RELATED ELECTROMAGNETIC FIELD ON PACEMAKERS
Get PDFThe patients with implanted pacemaker or cardioverter-defibrillator are exposed to a certain risk of affecting this device by surrounding electromagnetic field. There are many sources of potential risky electromagnetic fields, arc welding is definitely one of them. The aim of this article is to present research focused on analysis of the pacemaker function during welding. There were performed in-vitro measurements with 9 pacemakers during metal inert gas (MIG) and tungsten inert gas (TIG) method arc welding. The responses of pacemakers were monitored by communication via programmer. Based on these measurements there are proposed safe distances from the main parts of welding machines, and also conditions and instructions for arc welding by patients with pacemakers. To ensure patient safety, patients should maintain suggested safe distances, use direct current with minimal possible amplitude, and weld in short intervals. Additionally, their pacemakers should be set to bipolar configuration
Verification of window properties after 10 years of exploitation: results of measurements in the pavilion laboratory and the climate chamber
Get PDFThe article will deal with the analysis of measured data on a plastic window with thermal insulating triple glazing, which is suitable for low-energy or passive houses. The window was installed in 2011 in the test laboratory of the Department of Building Engineering and Urban planning, Faculty of Civil Engineering, University of Žilina (Slovakia), where it was tested under standard indoor climate conditions and real outdoor climate conditions. Surface temperatures on the frame friezes and glass system and heat flux density were recorded at a five-minute time step. In 2020, the window was removed from the laboratory and subsequently tested in a climate chamber. This paper will present the results of these measurements in terms of heat flow density waveforms, heat transfer coefficient, and total solar transmittance through the glazing. Subsequently, a simulation model of this window will be created in the environment of a computational program and its verification based on the measurements will be carried out. A series of calculations will be performed on the tuned model and analyses of the results and comparisons will be presented under the same climatic conditions as during the real measurements recorded by the meteorological station
Load carrying capacity of masonry arch railway bridges at the serviceability limit state
Get PDFThis article focuses on masonry arch railway bridges. The main topic is the algorithm, which was developed for the purpose of a non-linear arch bridge analysis. The sensitivity analysis of the input parameters of the calculation was carried out. Subsequently, the study was carried out for the comparison of four calculation methods. For this comparison, a set of arch bridges were chosen. Two methods used commercial software, and the other two methods were developed. One of the developed algorithms uses a simple linear calculation. The second developed algorithm uses an iterative approach to handle material and geometrical non-linearity. The first commercial software method uses 2D non-linear models, the second method is a limit collapse analysis using the software LimitState:RING. These three methods were developed to handle the SLS (serviceability limit state) criteria, and their results were compared to the result of LCC at the ULS (ultimate LS) using LimitState:RING
Experimental verification of the efficiency of selective non-catalytic reduction in a bubbling fluidized bed combustor
Get PDFControlling nitrogen oxide (NOX) emissions is still a challenge as increasingly stringent emission limits are introduced. Strict regulations will lead to the need to introduce secondary measures even for boilers with bubbling fluidized bed (BFB), which are generally characterized by low NOX emissions. Selective non-catalytic reduction has lower investment costs compared to other secondary measures for NOX reduction, but the temperatures for its efficient utilization are difficult to achieve in BFBs. This paper studies the possibility of an effective application of selective non-catalytic reduction (SNCR) of nitrogen oxides in a pilot-scale facility with a bubbling fluidized bed. The effect of temperatures between 880 and 950 °C in the reagent injection zone on NOX reduction was investigated. For the selected temperature, the effect of the amount of injected reagent, urea solution with concentration 32.5%wt., was studied. The experiments were carried out using 500 kWth pilot scale BFB unit combusting lignite. In addition, an experiment was performed with the combustion of wooden pellets. With reagent injection, all experiments led to the reduction of nitrogen oxides and the highest NOX reduction of 58% was achieved