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Rebar-Concrete Debonding Effect on the Seismic Performance of Reinforced Concrete Shear Walls: An Experimental Study
Full text linkDiverse criteria are taken for seismic design of shear walls due to their buckling failure in various regulations. Despite extensive studies on the topic, no practical mechanism has been widely adopted to effectively mitigate out-of-plane buckling in reinforced concrete shear walls. This study presents a novel approach to address this issue by experimentally investigating the effect of rebar-concrete debonding on the seismic performance of boundary elements in shear walls with minimum reinforcement. Plastic sleeves, applied to rebar at varying lengths (80 mm, 150 mm, and 220 mm), were used to induce debonding and thus modify the stress transfer mechanisms and crack propagation within the concrete. Five experimental samples of shear wall boundary element were designed and constructed with minimum reinforcement. Samples were subjected to non-uniform cyclic loading to study rebar debonding effect on crack distribution, rebar strain, and out-of-plane instability in boundary element. The results indicate that debonding leads to a reduction in the lateral stiffness of the boundary elements, postponing rebar buckling, and also provides a 12% enhancement in the tensile capacity of the rebar. Findings illustrate rebar-concrete debonding results in a reduction in lateral stiffness of boundary element. Similarly, comparing to a debonding free element, buckling member occurs at more minimal strains. It is also revealed that to prevent buckling, larger dimensions are required for sleeved sample. Moreover, robust evidence proved that increasing rebar debonding length enlarges crack width near sleeves, while sleeve length does not affect the first buckling or axial length of samples. This study provides a practical and innovative mechanism for addressing buckling challenges in minimum-reinforcement boundary elements, contributing to safer and more efficient structural design practices
Experimental Verification of the Influence of the Quality of Input Images on the Processing of the Photogrammetric Model
Full text linkPhotogrammetric acquisition and subsequent data processing has become increasingly common in recent years. However, this method of documentation is affected by many circumstances that can negatively influence the results. This paper is devoted to the experimental determination of the influence of the quality of input images on the processing of a photogrammetric model, because the quality of input images is essential for the accuracy of the final product and can be influenced by various factors. The effect of different image quality on the ability of software to align these images and on the accuracy of this alignment and subsequent processing of was tested practically in this case. Three specific interior surfaces and three specific exterior surfaces were used for the experiment, each of which was photographed in four series - one series was taken with high quality images, while the remaining three were specifically degraded in quality. Three photogrammetric software, Agisoft Metashape Professional, iTwin Capture Modeler and Pix4Dmapper, were selected for processing. In all software, all acquired series were processed and the ability to perform image orientation and the subsequent quality of this orientation was mainly monitored, where reprojection error was the main criterion. In the case of successfully aligned series, a dense point cloud was produced, which was also subjected to analysis. Based on these results, appropriate procedures for photogrammetric processing were determined when conditions that may negatively affect image quality are known in advance.
A Comparative Study of Breast Cancer Detection and Recurrence Prediction Using CatBoost Classifier
Full text linkIn 2019, breast cancer accounted for over one-third of all cancer cases in women in Iraq. It affects both men and women, though it is more common in women. This study delves into advanced machine learning techniques – CatBoost, XGBoost, Random Forest, SVM, KNN, and Naive Bayes – to improve the detection and prediction of breast cancer recurrence after healing. The goal is to evaluate models using key metrics (sensitivity, specificity, precision, F1 score, accuracy, ROC, and AUC score). Among all algorithms examined, CatBoost stood out, showcasing AUC values above 98 %, 90 %, and 83% on different datasets. This research demonstrates how machine learning techniques can significantly improve the accuracy of breast cancer detection and recurrence prediction, steering healthcare providers towards better patient care outcomes and more effective treatment plans
Design of the vertical trajectory for arrival and departure routes at Prague airport
Full text linkNumerous operational methods and related research focus on the efficient use of controlled airspace and thus on the management of its capacity. During the optimisation processes, various legislative limitations or technological constraints might appear. As the aviation industry continues to evolve, it occasionally happens that one of these pillars lags behind the other. This research focuses on a relatively underexplored aspect of using vertical profiles of air traffic service routes within the TMA Praha to optimise traffic flow in terms of flight efficiency and environmental impact.Virtual points, defining the aircraft’s vertical position limits along the given route, were computed to establish a vertical profile on already published standard departure or arrival routes. These points define the aircraft’s vertical position limits along the given route. Along with the proposal of a vertical profile, newly designed arrival and departure routes were implemented into the air traffic control simulation tool Escape Light and validated simultaneously within X-Plane simulator. Simulation studies conducted in these environments demonstrated significant fuel savings, averaging 13.2 %, with even greater savings observed in the Boeing 737-800, exceeding 25 %. These results confirm that applying vertical profiles positively impacts fuel consumption and contributes to more environmentally friendly operations
Abrupt change detection in railway noise data
Full text linkCurrent methods for diagnosing the quality of the railway superstructure are mainly based on optical sensors, which are relatively expensive compared to acoustic sensors. As part of the HLUKOS research project, a pair of microphones is installed near the wheel-rail contact point on a diagnostic vehicle of the Railway Administration (Czech railway infrastructure manager). The research task is to detect when the sound level changes significantly. A likelihood ratio method has been used in this paper to detect abrupt changes, which is a current scientific topic. Experiments with different input thresholds are performed on a sample of 250 m of track data. Initial experimental results show that this method is meaningfully able to detect locations of abrupt changes with input threshold values h = 4.58 and number of steps from N = 5 to N = 40
Comparison of bicycle detection methods in Prague traffic
Full text linkThe paper focuses on the detectors used to detect bicycles. It contains research part which describes various methods of bicycle detection and their possible advantages and disadvantages. The other part focuses on testing the methods under real conditions. Testing on 32 different location was conducted. The data from these tests were used to select the appropriate technology for each specific use case. The results show that current detectors are not the best option for bicycle detection and that videodetection and piezoelectric strips are the best way to go
THE DIMENSIONAL ACCURACY OF PROVISIONAL DENTAL REPLACEMENTS MADE BY DIFFERENT TECHNOLOGIES
Full text linkThe accuracy and quality of temporary dentures are important factors in dentistry, especially when bridging the time between tooth preparation and the placement of definitive dentures. The aim of this study is to determine the dimensional accuracy of temporary dental prostheses, specifically crowns and bridges, manufactured using different technologies. Three manufacturing methods were evaluated: stereolithography (SLA), digital light processing (DLP) and CNC milling. A total of 30 temporaries (n = 30) were fabricated, with an equal number fabricated using each technology. The fabricated samples were scanned with an S900 Arti 3D scanner (Zirkonzahn, Italy) and the scanned data was analyzed using GOM Inspect software (Zeiss, Germany) to detect deviations from the original model. The results showed that SLA technology showed the smallest deviations (0.025 ± 0.002 mm), indicating the highest accuracy among the tested technologies. DLP technology demonstrated medium accuracy (0.052 ± 0.011 mm), exceeding CNC milling, but not reaching SLA accuracy. Conversely, CNC milling showed the largest deviations (0.106 ± 0.009 mm) and the lowest accuracy in the production of temporary dentures. Based on the accuracy of the produced crowns and bridges, the SLA technology is therefore considered the most suitable for the creation of temporary dentures. These findings underscore the potential of SLA technology in achieving higher precision in dental applications, while offering a reliable method to produce quality temporary dental restorations
Method of lines for reaction-diffusion systems admitting invariant regions
Full text linkSystems of nonlinear reaction-diffusion equations arise in various fields, including chemistry, population dynamics, pattern formation, phase transitions, and image processing. With the exception of few analytically solvable cases, they are treated by numerical methods carefully adjusted to capture the nonlinear phenomena exhibited by the solution. This article shows how to extend the notion of invariant regions generalizing the maximum principle for diffusion equations to the finite-difference method of lines, and how to consequently prove convergence of the underlying numerical scheme. We also provide two particular examples of reaction-diffusion systems in one-dimensional space with a diagonal diffusion operator, which are solved by the presented numerical method
Foreword to the Memorial Issue of prof. Miloslav Havlíček
No full textMiloslav Havlíček2. 11. 1938 - 4. 9. 2024
This issue of Acta Polytechnica is dedicated to the memory of Professor Miloslav Havlíček who passed away a year ago. The role of this introduction is not to recollect his carrier; for that we refer to the biographical sketch by Rutwig Campoamor Stursberg. Our aim is rather to recall Miloslav\u27s vital role in the birth and growth of mathematical physics activities in our country. Being a disciple of Professor Votruba, he belonged to the generation of the first graduates of the newly founded Faculty of Technical and Nuclear Physics. As the most mathematically orientated among them, he always strove for a rigorous approach to physical problems. This came naturally in the 1960s when algebraic problems, close to his heart, were symbiotic with the quantum theory, but he kept this attitude for all his life irrespective of how the scientific scene was changing. What mattered was his "attractive force“, the ability to gather a group of peers and young people who share common interests. This was not without obstacles and not only due to his physical handicap coming from an infliction he suffered at the adolescent age, but also due to the adversity of some politically reinforced colleagues in the two horrible decades. Despite the bad weather, he founded at the end of that period a mathematical physics seminar which exists today and is one of the focal points of the discipline in our country. When the regime changed and he was called to restore the proper academic environment, he founded around the seminar the Doppler Institute for mathematical physics, which has flourished now for more than thirty years. The importance of Miloslav\u27s work for our mathematical physics community is difficult to overestimate. His openness to new ideas and ability to get to the core of the problem helped two generations grow and find their place in the research landscape. We remember him with deep gratitude. 
Subtractive gamma discrimination technique for neutron diamond detectors operating in mixed radiation fields
Full text linkA detection system based on diamond detectors and subtractive discrimination was developed for the measurement of thermal neutrons flux distribution changes during rod drop transient at the VR-1 reactor. The detection system was modified to replace the pulse-shaped method used for discrimination. The electronics available at the department was not able to measure high count rates with the pulse shape discrimination method. Subtractive discrimination allows us to reduce the requirements in the signal processing area, as the shape does not need to be recorded, and therefore the digitizer performance can be significantly lower. For this reason, a pulse stretching amplifier was developed and tested