169 research outputs found
A comparative study about the effects of linear, weakly and fully nonlinear wave models on the dynamic response of offshore wind turbines
No full textThe present work aims at comparing the dynamic response of a fixed–bottom offshore wind turbine subjected to the combined wind–waves action employing different nonlinear irregular wave kinematic models. To this purpose, linear, second–order and fully nonlinear models are implemented in the hydrodynamic module of a global hydro-aero-elastic solver. All the wave models are based on the potential flow assumption. The fully nonlinear wave kinematics is reproduced both on the full simulation time and, in order to save com- putational time, only on some space-time subdomains within a domain decomposition strategy. This approach permits achieving a much higher accuracy in the assessment of the hydrodynamic loads keeping the global computational effort similar to the one required by linear or weakly nonlinear models. The paper represents a preliminary investigation aimed at establishing to what extend the second–order wave model can efficiently capture the system response even when the system is exposed to moderate sea states. Moreover, a comparison between the four wave models seems to reveal that some resonant oscillations of the tower are triggered by nonlinear components higher than the 2nd–order. Hydrodynamic loads associated to the four wave models are coupled with aerodynamic loads acting on the rotor of a 5-MW wind turbine. Hydro-aero-elastic calculations are performed using the NREL open-source software FAST
A seismic retrofitting design approach for activating dissipative behaviour of timber diaphragms in existing unreinforced masonry buildings
No full textThe region of Groningen (NL) has experienced increasing human-induced seismicity caused by gas extraction in the last decades. The local building stock, not designed for seismic loads, consists for more than 50% of unreinforced masonry buildings with timber diaphragms. In this context, a detailed seismic characterization of timber and masonry structural components has taken place, and a retrofitting technique for timber floors activating their energy dissipation has been developed. Besides, specific analytical and numerical modeling strategies for as-built and retrofitted timber floors have been formulated. This work presents a design approach for creating strengthened dissipative timber diaphragms, and maximizing the seismic capacity of existing masonry buildings through this retrofitting method. The results from the performed numerical analyses prove that the proposed design approach for timber floors can increase the energy dissipation capacity of masonry buildings, while improving the box behavior at both damage and near-collapse limit state.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.Bio-based Structures & Material
Semantic Enrichment of Scientific Documents with Semantic Lenses – Developing methodologies, tools and prototypes for their concrete use
No full textCon questa dissertazione di tesi miro ad illustrare i risultati della mia ricerca nel campo del Semantic Publishing, consistenti nello sviluppo di un insieme di metodologie, strumenti e prototipi, uniti allo studio di un caso d‟uso concreto, finalizzati all‟applicazione ed alla focalizzazione di Lenti Semantiche (Semantic Lenses)
Cancer Exosomes as Conveyors of Stress-Induced Molecules: New Players in the Modulation of NK Cell Response.
No full textNatural killer (NK) cells are innate lymphoid cells that play a pivotal role in tumor surveillance. Exosomes are nanovesicles released into the extracellular environment via the endosomal vesicle pathway and represent an important mode of intercellular communication. The ability of anticancer chemotherapy to enhance the immunogenic potential of malignant cells mainly relies on the establishment of the immunogenic cell death (ICD) and the release of damage-associated molecular patterns (DAMPs). Moreover, the activation of the DNA damage response (DDR) and the induction of senescence represent two crucial modalities aimed at promoting the clearance of drug-treated tumor cells by NK cells. Emerging evidence has shown that stress stimuli provoke an increased release of exosome secretion. Remarkably, tumor-derived exosomes (Tex) produced in response to stress carry distinct type of DAMPs that activate innate immune cell populations. Moreover, stress-induced ligands for the activating receptor NKG2D are transported by this class of nanovesicles. Here, we will discuss how Tex interact with NK cells and provide insight into their potential role in response to chemotherapy-induced stress stimuli. The capability of some "danger signals" carried by exosomes that indirectly affect the NK cell activity in the tumor microenvironment will be also addressed
Influence of Molecular Weight of Vinylester Resins Toughened with Reactive Liquid Rubbers
No full textInfluence of knots and density distribution on compressive strength of wooden foundation piles
No full textThis work investigated the influence of knots on the compression strength of wooden foundation piles. The study involved 110 pile segments sawn from 18 spruce and 9 pine piles with a mean diameter of approximately 200 mm, and moisture contents above fiber saturation. The mechanical properties were determined performing both full-scale compression tests on pile segments, and small-scale experiments on discs sawn from selected segments, considering samples with and without knots. A knot ratio (KR) was defined analysing the knots layout of each wooden pile, and evaluating how the compressive strength was influenced by size, number and layout of knots. As final step, a prediction model was implemented based on the dry density and KR of wooden piles, to estimate the influence of knots on their compressive strength.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.Bio-based Structures & Material
Detuning CD8+ T lymphocytes by down-regulation of the activating receptor NKG2D: role of NKG2D ligands released by activated T cells.
No full textNKG2D is an activating receptor expressed on CD8(+)alpha beta(+) T cells, alpha beta(+) T cells, natural killer (NK) cells, and some CD4(+) T cells. For a long time, the interaction of NKG2D with its ligands (NKG2DLs) MICA, MICB, and ULBP1-3 has been considered a mechanism for recognition and elimination of tumor, infected, or otherwise "stressed" cells. However, a new role for NKG2D as an immunoregulatory receptor is emerging. Here, we show that NKG2D is strongly down-modulated on antigen-activated CD8(+) T cells but only if CD4(+) T cells are present. Down-modulation was caused by soluble factors produced by CD4(+) T cells, and in particular soluble NKG2DLs were found in the supernatants of antigen-activated T-cell cultures. MICB was the ligand released at higher levels when CD4(+) T cells were present in the cell cultures, suggesting that it could be the major player of NKG2D down-modulation. CD8(+) T cells expressing low levels of NKG2D had impaired effector functions, as evaluated by proliferation, cytokine production, and cytotoxicity assays after combined triggering of NKG2D and TCR-CD3 complex. These findings show that activated CD4(+) T cells expressing NKG2DLs can efficiently prevent NKG2D-mediated CD8(+) T-cell functions, and suggest that the NKG2D/NKG2DL interaction can regulate immune responses. (Blood. 2009; 113: 2955-2964
Real-time health monitoring of civil structures by online hybrid learning techniques using remote sensing and small displacement data
No full textStructural Health Monitoring (SHM) has become an essential topic in most of the modern societies due to critical importance of economic and human losses caused by occurring damage. To avoid any catastrophic event such as partial and global collapse in vital civil structures, many data-based methods under the concepts of artificial intelligence and machine learning using various types of sensing technologies have been proposed and developed. The main objective of such techniques is to learn a computational or statistical model/machine by using sufficient training data during a fixed training period in an offline or batch learning manner. On this basis, in the learning process, one assumes that the training period is sufficiently long to capture all possible environmental and/or operational variations and no damage occurs. However, these assumptions may be problematics due to some major limitations. First, there is no guarantee that new measured data out of the training time has the same variability condition during the learning process. Second, it is illogical to suppose that the structure does not suffer from damage within a long monitoring process. On the other hand, SHM via Synthetic Aperture Radar (SAR) images from the remote sensing technology has become popular among civil engineers. However, an SAR-based SHM strategy itself contains major challenges that should be dealt with. Due to some limitations in SAR images, most of the SHM projects via this technology incorporate a few images, even in long-term monitoring. On the other hand, the majority of research studies in this category is based on directly analyzing displacement samples extracted from SAR images. Under such circum- stances, the process of health monitoring of a complex and vital civil structure may not lead to reasonable consequences owing to considering insufficient small displacement data from SAR images and direct data analysis. To deal with the aforementioned challenges and limitations, this article proposes online hybrid learning methods to detect damage via small displacement data from SAR images. A small set of displacement samples extracted from satellite images of TerraSar-X is then used to assess accuracy and performance of the proposed online hybrid method and compare them with some existing state-of-the-art techniques. Results show that the proposed method is successful in pre-collapse prediction of the bridge even under strong EOV conditions
Topologically optimized structural glass megaliths: Potential, challenges and guidelines for stretching the mass limits of structural cast glass
No full textThis paper introduces the use of structural topology optimization (TO) as a new design approach that enables the creation of monolithic load-bearing cast glass components of substantial dimensions with significantly reduced annealing times, rendering such components viable in terms of manufacturing. Using topology optimization, the glass mass can be optimized to match design loads whilst maintaining high stiffness and a homogeneous mass for even cooling. Initially, the two main TO approaches are discussed in terms of suitability for cast glass. A strain-based optimization is eventually preferred over Von Mises optimization in the specific study. To explore the potential of TO for optimizing structural cast glass components, three distinct studies are analyzed in ANSYS workbench: (i) a structural glass node, (ii) a cast glass floor and (iii) a pedestrian bridge. These lead to the establishment of a set of design/input criteria, taking into account glass as a material, casting as a manufacturing method, addressing also the safety of the structure. The design studies also reveal the inherent challenges of using TO for load-bearing glass components, which, in turn, lead to the establishment of design guidelines for developing a TO tool specifically for glass. Towards the real-life applicability of such complex-shaped, customized components, possible manufacturing methods are also discussed.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.Structural Design & MechanicsTeachers of Practice / AE+TCivil Engineering & GeosciencesArchitecture and the Built EnvironmentApplied Mechanic
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