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Influence of various angles and distances on luminance measurement results
Full text linkThe behaviour of drivers in nocturnal conditions is primarily influenced by the early detection of obstacles within the roadway. A reliable approach to evaluate night-time traffic environments is through luminance analysis. This study aimed to investigate the impact of conducting luminance measurements at reduced distances compared to those specified by standard guidelines. Additionally, the study examined the effect of the measurement angle of the luminance analyser on the recorded luminance values. The findings indicate that the measurement angle is a critical factor for ensuring accurate luminance readings, while the distance between the analyser and the measured surface has minimal influence on the results. Statistical analysis confirms that reliable data can be obtained even when deviating from standard measurement conditions. These results suggest that luminance analysis is feasible and applicable across a wide range of traffic scenarios
The effect of roadside on speed perception
Full text linkThe study examines how various roadside elements, such as flat areas, trees, slopes, and buildings, influence speed perception. Data from multiple previous studies were combined and reanalyzed using newly established criteria to assess the proximity and nature of roadside features. The dataset includes 9 776 speed estimates, gathered from a wide range of road types and surroundings, allowing for an analysis of how these elements affect speed estimation accuracy.The findings suggest that flat areas consistently lead to overestimations of speed, likely due to the lack of physical cues that provide visual references. In contrast, trees and forested environments have a stabilizing effect, helping individuals to estimate speed more accurately. Built environments, such as industrial zones and urban areas, tend to lead to significant overestimations of speed. These results highlight the importance of roadside environments in influencing speed perception, with natural settings like forests providing clearer visual cues that help drivers and observers better estimate speed
Calculation of queue formation and queue length at airport check-in counters
Full text linkThis paper focuses on calculation of airport passenger queue formation and its length. The main goal of the paper is to evaluate the appropriateness of the combination of machine learning and determistic algorithm for queue length determination. The study focuses on the departing passenger flows to the check-in counters. In this study the Random Forest algorithm was applied for passenger number prediction, and followed by application of the deterministic algorithm for passenger queue length estimation. The study was performed using the real data from the Václav Havel Airport Prague operations. Presented results indicate that the combined approach of machine learning and a deterministic algorithm offers useful insights into passenger queue formation. This approach provides valuable insights into queue dynamics at check-in counters, enabling improvements in planning and management of airport operations during operational peak
Static performance analysis of prestressed Π-type beam cable-stayed bridge cable damage
Full text linkWith the increasing span of cable-stayed bridges, the self-weight of the structure accounts for a large proportion. The π-type beam, due to its small cross-sectional area, can significantly reduce the self-weight and cost. It is suitable for double-cable surface system cable-stayed bridges and has therefore experienced rapid development. This paper takes a prestressed π-type beam cable-stayed bridge in China as an engineering example, and focuses on the overall and local parameter sensitivity of the structure, as well as the force characteristics under cable damage. The main factors causing cable damage in prestressed π-type beam cable-stayed bridges are analyzed, and the selection of elastic modulus as the damage variable is determined. Based on the finite element model analysis of the actual bridge, different cable damage simulations are selected to analyze the static variations of the main beam and cables caused by single-side, symmetrical, and asymmetrical cable damage, as well as the dynamic variations of the overall bridge. This analysis provides a reference for the mechanical performance analysis of prestressed π-type beam cable-stayed bridges under similar cable damage conditions in the future
Chance constrained stochastic programming in design of a frame structure
Full text linkA civil engineering problem concerning an optimal design of a loaded frame structure with random Young\u27s modulus is discussed. The developed multi-criteria optimization model involves ODE-type constraints and also one chance constraint related to the structure’s reliability. A computational scheme for this type of problems is proposed using the finite difference method for the approximation of the ODE constraint and the scenario-based approach for a random variable approximation. The chance constraint is handled by two approaches – analytical approach and penalty reformulation. An a posteriori check of satisfying the chance constraint is made and the upper bounds of the obtainable reliability are computed
An Analytical Investigation on Nonlinear Free Vibrations of Beam with a Fatigue-Crack
Full text linkThis study examines the nonlinear free vibration behavior of beams affected by a fatigue crack. Initially, transverse vibrations of a cantilevered beam are demonstrated as a single-degree-of-freedom system with equivalent mass and stiffness in the first mode. Subsequently, a novel bilinear stiffness model for beams with breathing cracks is introduced. Utilizing this model, the governing differential equation is formulated analytically using the Lindest-Poincaré perturbation method. The results indicate that the response derived through the perturbation method comprises 2 distinct components. With stiffness equal to the mean of the crack\u27s completely open and fully closed states, the first component depicts the system\u27s reaction. The additional correction terms, supplementing the initial response, account for variations in stiffness resulting from crack opening and closing dynamics. These corrections elucidate the impact of changing equivalent stiffness on the system\u27s response due to crack dynamics. Indeed, the correction terms encompass higher harmonic components that emerge in the response, stemming from the nonlinear behavior of the structure. These additional terms capture the intricate interplay between crack dynamics and system response, providing a comprehensive understanding of the system\u27s nonlinear characteristics
Flexural analysis of steel mesh reinforced polyurethane concrete material
Full text linkIn this paper, a new method of steel mesh reinforced polyurethane concrete (SMPUC) material for bridge reinforcement is proposed because of the peeling failure of the reinforced layer of steel mesh reinforced polymer mortar (SMPM) material. Using the excellent anti-corrosion and tensile properties of high-strength steel mesh, as well as the advantages of strong adhesion and fast curing speed of polyurethane concrete, the two materials are combined together. In order to verify the feasibility of this strengthening method, the mechanical properties of SMPUC material are investigated by bending test of SMPUC material sheet. The main factors affecting the tensile properties of the composites are analyzed by considering the test variables such as specimen width, specimen thickness, glue-powder ratio and curing time. Based on the simplified tension model of high strength steel wires and the stress-strain relationship between tension and compression of polyurethane concrete, the calculation method of flexural bearing capacity of composite materials is obtained. The test results show that the flexural strength of the composite can be improved by increasing the width of the specimen, and the deflection can be reduced by increasing the reinforcement ratio, while the influence of the glue-powder ratio on the deflection is small
Assessment of the effects of UV-A exposure on the mechanical strength of offshore mooring multifilaments
Full text linkThe offshore industry faces significant challenges in the dynamic energy and maritime domain, necessitating robust engineering solutions for mooring systems. This study investigates the impact of ultraviolet radiation A (UV-A) on the mechanical strength of high-strength multifilaments, crucial for offshore mooring. Five fibre types: Aramid, High-modulus polyethylene (HMPE), Liquid crystal polymers (LCP), Polyamide and Polyester, are exposed to UV-A for up to 28 days. Initial mechanical characterisation provides baseline data, while subsequent tests reveal varying degrees of degradation. Polyamide and polyester exhibit superior stability, while Aramid and HMPE show restrained degradation. LCP experiences substantial degradation. Mathematical modelling reveals distinct degradation patterns, emphasising the need for comprehensive understanding in ensuring the safety and efficiency of offshore operations. There are indications that degradation by ultraviolet exposure for Aramid, HMPE, polyamide, and polyester fibres, restricts the constitutive behaviour in terms of strength and extension, but without changing the shape of the curve. These findings provide valuable insights for the offshore industry and guidance future research and development efforts
Czech contribution to AHEAD2020: novel/alternative X-ray optics
Full text linkWe briefly present selected results in the field of X-ray optics obtained within the project at the CTU in Prague in collaboration with other Czech Institutes, mainly Rigaku Prague, where X-ray optics modules were assembled. These efforts covered the simulations and designs of LE (Lobster Eye) and KB (Kirkpatrick-Baez) optical Systems, a study of new and alternative simulation/ray tracing methods, studies of alternative/improved coatings, studies of improved substrates (Si and float glass), design and assembly of new test modules where both LE and KB test modules were based on Multi Foil Technology (glass and Si substrates < 1mm) finished by tests in visible light and X-rays
QUANTITATIVE METHODS FOR MEASURING PATIENT PREFERENCES: PILOT STUDY FOR PATIENTS WITH LOCALIZED PROSTATE CANCER
Full text linkThis pilot study examines patient preferences in patients with localized prostate cancer using quantitative methods for measuring Discrete Choice Experiment (DCE) and Best-Worst Scaling (BWS) type 3. The study focuses on key attributes that may influence patients\u27 treatment decisions. Patients chose one of two or three hypothetical treatment scenarios based on key attributes: risk of erectile dysfunction; urinary incontinence; other side effects; transport to hospital and return to normal activities. Additionally, patients evaluated both methods in terms of difficulty and satisfaction using a Likert scale. Results show that the most important attribute for patients with localized prostate cancer is the risk of erectile dysfunction (36.0%, 29.8%), followed by the risk of urinary incontinence (24.9%, 23.0%). In both attributes, patients wanted to avoid the worst levels and vice versa. The results of preferred attributes did not differ between methods. Patients found the Discrete Choice Experiment method less difficult and were more satisfied with it. This research suggests that quantitative approaches, such as DCE and BWS, can be valuable tools for better understanding patient preferences and integrating them into personalized treatment decision-making