130 research outputs found

    On the Images of Sails appeared in Ancient Literature

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    Background: Stress calculations in atherosclerotic coronary vulnerable plaques can aid in predicting coronary cap rupture. In vivo plaque geometry and composition of coronary arteries can merely be obtained via intravascular imaging. Only optical driven imaging techniques have sufficient resolution to visualize the fibrous cap, but due to limited penetration depth deeper components such as the backside of the necrotic core (NC) are generally not visible. The goal of this study was to investigate whether peak cap stresses can be approximated by reconstructing the backside of the NC. Methods: Manual segmentations of coronary histological cross-sections served as a geometrical ground truth and were obtained from seven patients resulting in 73 NCs. Next, the backside was removed and reconstructed according to an estimation of the relative necrotic core thickness (rNCt). The rNCt was estimated at three locations along the NC angle and based on either group averaged parameters or plaque specific parameters. Stress calculations were performed in both the ground truth geometry and the reconstructed geometries and compared. Results: Good geometrical agreement was found between the ground truth NC and the reconstructed NCs, based on group averaged rNCt estimation and plaque specific rNCt estimation, measuring the NC area difference (25.1 % IQR 14.0-41.3 % and 17.9 % IQR 9.81-32.7 %) and similarity index (0.85 IQR 0.77-0.90 and 0.88 IQR 0.79-0.91). The peak cap stresses obtained with both reconstruction methods showed a high correlation with respect to the ground truth, r2 = 0.91 and r2 = 0.95, respectively. For high stress plaques, the peak cap stress difference with respect to the ground truth significantly improved for the NC reconstruction based plaque specific features (6 %) compared to the reconstruction group averaged based (16 %). Conclusions: In conclusion, good geometry and stress agreement was observed between the ground truth NC geometry and the reconstructed geometries. Although group averaged rNCt estimation seemed to be sufficient for the NC reconstruction and stress calculations, including plaque specific data further improved stress predictions, especially for higher stresses.ImPhys/Acoustical Wavefield Imagin

    Assessing economic risk, safety standards, and decision-making

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    Risk-informed decision-making needs methods for assessing flood risk, and often the flooding probability and the consequences of floods (such as economic damage and fatalities) play an important role in the risk assessment. Also, measures to reduce the flood risk need to be formulated, in order to make a risk-informed decision, whether to accept the risk or to implement measures to reduce or to transfer the risk. These measures can be technical (for example, storm surge barriers) but can also be in the area of spatial planning or crises management. The outcome of such a process might be formalized in a “safety standards,” which can be used for the design of measures. These standards show remarkable differences between the United States, the United Kingdom, and the Netherlands.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Hydraulic Structures and Flood Ris

    Kansen voor waterveiligheid

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    Hydraulic EngineeringCivil Engineering and Geoscience

    A look at future flood risk prospects: ideas of All-Risk researchers

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    Hydraulic Structures and Flood Ris

    A step towards functional integration: Reflection program case ‘Rotterdam roof park’

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    Many functions are combined in the Rotterdam Roof Park project: It is a shopping mall, a parking garage, a park on the roof, and last but not least, a flood defense. The research in our program was done after the buildings and structures had been built. So the research projects were not hampered by the conflicting interests of stakeholders during the design and implementation process, as might sometimes be the case in so-called ‘action research’. Still, the case study of the Roof Park clearly shows the pros and cons of Multifunctional Flood Defenses Hydraulic Structures and Flood Ris

    Societal need for multifunctional flood defenses: Introduction

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    Prof.dr.ir. Matthijs Kok is Professor of Flood Risk at the Faculty of Civil Engineering and Geosciences at TU Delft; he was Program leader of the ‘Integral and Sustainable Design of Multifunctional Flood Defenses’ research program, funded by the Dutch Science and Technology Foundation STW. Presently, he is Program leader of the STW-Perspectief research program ‘All RISK’, which will study the implementation of new risk standards in the Dutch national flood protection program (2017-2022). Hydraulic Structures and Flood Ris

    Three Symmetries for Data-Driven Pedestrian Inertial Navigation

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    The last years have seen a growing body of literature on data-driven pedestrian inertial navigation. However, despite this, it is still unclear how to efficiently combine classical models and other a priori information with existing machine learning frameworks. In this paper, we first categorize existing approaches to data-driven pedestrian inertial navigation, including approaches where a machine learning algorithm is embedded into an overarching classical framework and purely data-driven frameworks. We then propose an estimation framework where navigation estimates obtained by classical means are fed to a machine learning algorithm which is trained to correct and improve the estimates. Further, we describe three symmetries that can be used to constrain the proposed estimation framework and thereby improve its performance. These are 1) the rotational symmetry of pedestrian dynamics, 2) the rotational symmetry of the sensors, and 3) the temporal symmetry of pedestrian dynamics. To demonstrate the usefulness of the proposed framework, we use data from foot-mounted inertial sensors utilizing zero-velocity updates under mixed walking and running. Machine learning corrections are implemented using both neural networks and Gaussian processes.Team Manon Ko

    Werken aan een veilige delta

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    De recente overstromingen in het buitenland (New Orleans, Thailand, Japan en New York) laten zien hoe groot de maatschappelijke ontwrichting na een overstroming is en wat het belang van een goed waterkeringssysteem is. Hoewel Nederland één van de best beveiligde delta’s in de wereld is, voldoet een derde van onze hoofdwaterkeringen niet aan onze wettelijke normen. De komende jaren is het van belang om onder meer in het hoogwaterbeschermingsprogramma en Deltaprogramma voortvarend vorm te geven aan uitwerking en implementatie van versterkingen. De overstromingsrisicobenadering kan helpen om te komen tot kosteneffectieve investeringen in hoogwaterbescherming.Water ManagementCivil Engineering and Geoscience

    Everything is bigger in Texas: Reflection program case ‘Houston Galveston Bay, Texas’

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    The saying goes that ‘Everything is bigger in Texas.’ This holds true for both the flood risk in the Houston-Galveston Bay Area, and for the complexity of issues that need to be dealt with in order to reduce it – assuming there is agreement that the current risk is unacceptable. There is currently no formal direction, and hence no preferred direction for designing a strategy for flood risk reduction Spatial Planning and StrategyHydraulic Structures and Flood Ris
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