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Automatic BIM-model creation of bridge structure using 3D-laser scanning, algorithms and parametric modeling
No full textBridges have a crucial and huge role in the safety of the public. An important aspect in maintaining the safety of a bridge structure is to have access to a BIM-model that can be used in analysis and facility management. Long-span spatial curved bridge structures with circular pipe components are widely used in engineering. Measuring the overall alignment of long-span spatial curved structures with circular pipe components quickly and accurately is an important aspect that increase the effectiveness of creating digital twins. This thesis has an approach to find a method to measure this overall alignment in an accurate and quick way.
The method in this thesis is applied to a real case study which is a pedestrian bridge located in Oslo, Norway. The bridge consists of curved steel members at top chord and circular pipe components as struts.
The method implements terrestrial 3D laser scanning of the case bridge for data collection. The data obtained from the scans has been processed and imported into MATLAB to extract geometry information of the components automatically by applying algorithms. The information and parameters extracted from MATLAB are then imported into Dynamo to generate a parametric driven BIM-model of the existing bridge. The model is compared with the point cloud of the bridge to analyze the deviation between the point cloud and the parametric driven BIM-model.
The results obtained from various operations have a good level of accuracy, but there are still room for adjustments in the method that can improve the accuracy of the results. The case study examination in this thesis was however successful, and it can be concluded that the method applied in this thesis can help to measure the overall alignment of long-span curved structures with circular pipe components quickly and accurately
Global Asymptotic Tracking for Marine Vehicles using Adaptive Hybrid Feedback
No full textThis paper presents an adaptive hybrid feedback control law for global asymptotic tracking of a hybrid reference system for marine vehicles in the presence of parametric modeling errors. The reference system is constructed from a parametrized loop and a speed assignment specifying the motion along the path, which decouples the geometry of the path from the motion along the path. During flows, the hybrid feedback consists of a proportional-derivative action and an adaptive feedforward term, while a hysteretic switching mechanism that is independent of the vehicle velocities determines jumps. The effectiveness of the proposed control law is demonstrated through experiments
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The more experienced, the better prepared? New evidence on the relation between teachers’ experience and their readiness for online teaching and learning
No full textIn the present study, we tested the common assumption that teachers with more experience consider themselves better prepared for online teaching and learning (OTL). Utilizing the data from a survey of 366 higher-education teachers from Portugal at the beginning of the COVID-19 pandemic in 2020, we performed structural equation modeling to quantify the experience-readiness relationship. The survey contained an assessment of teachers' OTL readiness which was measured by their perceptions of the institutional support, online teaching presence, and TPACK self-efficacy. In contrast to the linearity assumption “the more experienced, the better prepared”, we found robust evidence for a curvilinear relationship. Teachers’ readiness for OTL increased first and then decreased with more experience—this applied especially to the self-efficacy dimension of readiness. Further analyses suggested that the experience-readiness relationship does not only exist at the level of aggregated constructs but also at the level of indicators, that is, specific areas of knowledge, teaching, and support. We argue that both novice and experienced teachers in higher education could benefit from experience-appropriate, pedagogical, and content-related support programs for OTL
Data-driven simultaneous identification of the 6DOF dynamic model and wave load for a ship in waves
No full textIn marine operations, the performance of model-based automatic control design and decision support systems highly relies on the accuracy of the representative mathematical models. Model fidelity can be crucial for safe voyages and offshore operations. This paper proposes a data-driven parametric model identification of a ship with 6 degrees of freedom (6DOF) exposed to waves using sparse regression according to the vessel motion measurements. The features of the complex ship dynamics are extracted and expressed as a linear combination of several functions. Thruster inputs and environmental loads are considered. The hydrodynamic coefficients and wave-induced loads are simultaneously estimated. Unlike earlier studies using a limited number of unknown functions, a library of abundant candidate functions is applied to fully consider the coupling effects among all DOFs. The benefit of the proposed method is that it does not require the exact construction of the library functions. Based on the estimated model, short-term motion prediction is achievable. The algorithm is verified through experiments. The method can be extended to other types of floating structures
Total dominator chromatic number of k-subdivision of graphs
No full textLet G be a simple graph. A total dominator coloring of G, is a proper coloring of the vertices of G in which each vertex of the graph is adjacent to every vertex of some color class. The total dominator chromatic (TDC) number χdt(G) of G, is the minimum number of colors among all total dominator coloring of G. For any k ∈ ℕ, the k-subdivision of G is a simple graph G1/k which is constructed by replacing each edge of G with a path of length k. In this paper, we study the total dominator chromatic number of k-subdivision of G
Genotoxic effects of occupational exposure to glass fibres - A human biomonitoring study
No full textAs part of a large human biomonitoring study, we conducted occupational monitoring in a glass fibre factory in Slovakia. Shopfloor workers (n = 80), with a matched group of administrators in the same factory (n = 36), were monitored for exposure to glass fibres and to polycyclic aromatic hydrocarbons (PAHs). The impact of occupational exposure on chromosomal aberrations, DNA damage and DNA repair, immunomodulatory markers, and the role of nutritional and lifestyle factors, as well as the effect of polymorphisms in metabolic and DNA repair genes on genetic stability, were investigated. The (enzyme-modified) comet assay was employed to measure DNA strand breaks (SBs) and apurinic sites, oxidised and alkylated bases. Antioxidant status was estimated by resistance to H2O2-induced DNA damage. Base excision repair capacity was measured with an in vitro assay (based on the comet assay). Exposure of workers to fibres was low, but still was associated with higher levels of SBs, and SBs plus oxidised bases, and higher sensitivity to H2O2. Multivariate analysis showed that exposure increased the risk of high levels of SBs by 20%. DNA damage was influenced by antioxidant enzymes catalase and glutathione S-transferase (measured in blood). DNA repair capacity was inversely correlated with DNA damage and positively with antioxidant status. An inverse correlation was found between DNA base oxidation and the percentage of eosinophils (involved in the inflammatory response) in peripheral blood of both exposed and reference groups. Genotypes of XRCC1 variants rs3213245 and rs25487 significantly decreased the risk of high levels of base oxidation, to 0.50 (p = 0.001) and 0.59 (p = 0.001), respectively. Increases in DNA damage owing to glass fibre exposure were significant but modest, and no increases were seen in chromosome aberrations or micronuclei. However, it is of concern that even low levels of exposure to these fibres can cause significant genetic damage
Energy potentials, negative emissions, and spatially explicit environmental impacts of perennial grasses on abandoned cropland in Europe
No full textCultivating perennial grasses on abandoned cropland for bioenergy production is a promising option to meet future renewable energy demands at lower risks for food security and environmental degradation. Studies on the potential environmental impacts of perennial grasses mostly focus on specific locations, while effects and potentials of a large-scale deployment on abandoned cropland are still unexplored. This work performs a spatially explicit life cycle assessment of agricultural production of three perennial grasses (miscanthus, switchgrass, and reed canary grass) on abandoned cropland in Europe under rainfed and irrigated conditions. We estimate the primary bioenergy potentials and potential environmental impacts on climate change (including soil organic carbon changes), freshwater and marine eutrophication, terrestrial acidification, fossil resource scarcity and water scarcity footprint. Under rainfed conditions, switchgrass has the largest supply potential (174 MtDM yr−1) while miscanthus has the lowest average climate impact (169 kg CO2 tDM−1). Irrigation increases biomass yields by 97% for miscanthus, 62% for switchgrass and 29% for reed canary grass, but climate change impacts per tDM increase by 24%, 32% and 44%. Water scarcity footprints also increase, ranging from 4.7 to 9 world m3eq. kgDM−1. When soil organic carbon changes are considered, the net climate effects turn to negative for all perennial grasses under rainfed conditions (and for miscanthus with irrigation as well), showing a potential for land-based negative emissions by storing carbon in soils while delivering renewable energy. Bioenergy potentials range between 1 and 7 EJyr−1 (corresponding to 1–10% of today's EU primary energy demand) and the scale of negative emissions can be up to −24 Mt. CO2-eq. yr−1 (equal to 5.6% of EU's agricultural sector emissions). The consideration of site-specific conditions for water supply and crop affinity can identify the best local agricultural practices for energy yields and negative emissions at reduced environmental trade-offs
Reconstruction of surface pressures on flat plates impacted by blast waves using the Virtual Fields Method
No full textAn accurate description of surface pressure loads imposed by blast waves is crucial for the design of the next generation of blast-resistant structures. However, experimental techniques for non-intrusive, full-field surface pressure measurements are not readily available. To address this challenge, a new application of the Virtual Fields Method (VFM) has been explored to reconstruct the surface pressures acting on thin steel plates using full-field deformation measurements of the plate dynamics. A shock tube facility was used to generate a blast-like loading in controlled, laboratory environments, where the plate dynamics were measured using the deflectometry technique. Different blockages at the shock tube exit allowed for varying the spatial distribution and temporal history of the blast loading. The surface pressures were reconstructed from experimentally measured kinematic fields using the VFM. A nearly non-deformable plate equipped with point-wise pressure sensors was also used to obtain a reference, allowing to assess the performance and reliability of the proposed methodology in capturing the surface pressure distributions. Moreover, visualizations of the different blast wave impacts on the plate were obtained using a background-oriented schlieren setup. Finally, the influence of potential error sources was investigated by means of a virtual laboratory using a finite element analysis to generate synthetic input to the load reconstruction analysis. The proposed methodology provided robust, precise predictions using noise-free input from virtual experiments. The presence of both systematic and random errors during the experimental campaign resulted in a reduced pressure reconstruction accuracy, where the peak pressure amplitudes were approximately 10–20% lower compared to the pointwise transducer data. Pressure reconstructions from experimental data still showed qualitatively good estimates of the pressure distributions that were extrapolated from transducer data. Hence, this work highlights the capabilities of a promising methodology to obtain more insight into the effective action of the loading during blast–structure interaction of plated structures.
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