Academic literature on the topic 'Towed foils'

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Journal articles on the topic "Towed foils"

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Roman, Chris, and Dave Hebert. "Concept Tests for a New Wire Flying Vehicle Designed to Achieve High Horizontal Resolution Profiling in Deep Water." Journal of Atmospheric and Oceanic Technology 28, no. 12 (December 1, 2011): 1657–71. http://dx.doi.org/10.1175/jtech-d-10-05040.1.

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Abstract Efficiently profiling the water column to achieve both high vertical and horizontal resolution from a moving vessel in deep water is difficult. Current solutions, such as CTD tow-yos, moving vessel profilers, and undulating tow bodies, are limited by ship speed or water depth. As a consequence, it is difficult to obtain oceanographic sections with sufficient resolution to identify many relevant scales over the deeper sections of the water column. This paper presents a new concept for a profiling vehicle that slides up and down a towed wire in a controlled manner using the lift created by wing foils. The wings provide a novel low-power method of propulsion along the cable by using the free stream velocity of the wire moving through the water in similar fashion to a sailboat sailing up wind. Scale model tests show a wide range of achievable profiling glide slopes for tow cable angles between vertical and 45°, and effective isolation of cable strum vibration from the towed vehicle body. The concept is not depth limited and will offer two-dimensional resolution that meets or exceeds current undulating tow bodies over the full water column. Additionally, this system could be used simultaneously with many other deep towed instrument packages to produce complementary datasets.
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Deng, Rui, Shigang Wang, Wanzhen Luo, and Tiecheng Wu. "Experimental Study on the Influence of Bulbous Bow Form on the Velocity Field around the Bow of a Trimaran Using Towed Underwater 2D-3C SPIV." Journal of Marine Science and Engineering 9, no. 8 (August 21, 2021): 905. http://dx.doi.org/10.3390/jmse9080905.

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In this study, particle image velocimetry was applied to measure the flow field around the bow region of a trimaran with different appendages. The dimensionless axial velocity u/U in test planes 1 and 2 of the testing model was measured by using a towed underwater stereoscopic particle image velocimetry (SPIV) system. Based on the measured flow field data, the local sinkage values in test planes 1 and 2 of the testing model with different appendages at speeds of 1.766 and 2.943 m/s were presented. In addition, the effects of speed, bulbous bow type, T foils, and bow wave on the axial velocity u/U were studied in detail. The acquired experimental data help in understanding the distribution of the flow field around the ship bow, and the data can also act as a reference to verify computational fluid dynamics (CFD) results.
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Steele, S. C., J. M. Dahl, G. D. Weymouth, and M. S. Triantafyllou. "Shape of retracting foils that model morphing bodies controls shed energy and wake structure." Journal of Fluid Mechanics 805 (September 20, 2016): 355–83. http://dx.doi.org/10.1017/jfm.2016.553.

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The flow mechanisms of shape-changing moving bodies are investigated through the simple model of a foil that is rapidly retracted over a spanwise distance as it is towed at constant angle of attack. It is shown experimentally and through simulation that by altering the shape of the tip of the retracting foil, different shape-changing conditions may be reproduced, corresponding to: (i) a vanishing body, (ii) a deflating body and (iii) a melting body. A sharp-edge, ‘vanishing-like’ foil manifests strong energy release to the fluid; however, it is accompanied by an additional release of energy, resulting in the formation of a strong ring vortex at the sharp tip edges of the foil during the retracting motion. This additional energy release introduces complex and quickly evolving vortex structures. By contrast, a streamlined, ‘shrinking-like’ foil avoids generating the ring vortex, leaving a structurally simpler wake. The ‘shrinking’ foil also recovers a large part of the initial energy from the fluid, resulting in much weaker wake structures. Finally, a sharp edged but hollow, ‘melting-like’ foil provides an energetic wake while avoiding the generation of a vortex ring. As a result, a melting-like body forms a simple and highly energetic and stable wake, that entrains all of the original added mass fluid energy. The three conditions studied correspond to different modes of flow control employed by aquatic animals and birds, and encountered in disappearing bodies, such as rising bubbles undergoing phase change to fluid.
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Kerdraon, Paul, Boris Horel, Patrick Bot, Adrien Letourneur, and David David Le Touzé. "High Froude Number Experimental Investigation of the 2 DOF Behavior of a Multihull Float in Head Waves." Journal of Sailing Technology 6, no. 01 (February 4, 2021): 1–20. http://dx.doi.org/10.5957/jst/2021.6.1.1.

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Dynamic Velocity Prediction Programs are taking an increasingly prominent role in high performance yacht design, as they allow to deal with seakeeping abilities and stability issues. Their validation is however often neglected for lack of time and data. This paper presents an experimental campaign carried out in the towing tank of the Ecole Centrale de Nantes, France, to validate the hull modeling in use in a previously presented Dynamic Velocity Prediction Program. Even though with foils, hulls are less frequently immersed, a reliable hull modeling is necessary to properly simulate the critical transient phases such as touchdowns and takeoffs. The model is a multihull float with a waterline length of 2.5 m. Measurements were made in head waves in both captive and semi-captive conditions (free to heave and pitch), with the model towed at constant yaw and speed. To get as close as possible to real sailing conditions, experiments were made at both zero and non-zero leeway angles, sweeping a wide range of speed values, with Froude numbers up to 1.2. Both linear and nonlinear wave conditions were studied in order to test the limits of the modeling approach, with wave steepness reaching up to 7% in captive conditions and 3.5% in semi-captive ones. The paper presents the design and methodology of the experiments, as well as comparisons of measured loads and motions with simulations. Loads are shown to be consistent, with a good representation of the sustained non-linearities. Pitch and heave motions depict an encouraging correlation which confirms that the modeling approach is valid.
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Wibawa, M. S., S. C. Steele, J. M. Dahl, D. E. Rival, G. D. Weymouth, and M. S. Triantafyllou. "Global vorticity shedding for a vanishing wing." Journal of Fluid Mechanics 695 (February 13, 2012): 112–34. http://dx.doi.org/10.1017/jfm.2011.565.

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AbstractIf a moving body were made to vanish within a fluid, its boundary-layer vorticity would be released into the fluid at all locations simultaneously, a phenomenon we call global vorticity shedding. We approximate this process by studying the related problem of rapid vorticity transfer from the boundary layer of a body undergoing a quick change of cross-sectional and surface area. A surface-piercing foil is first towed through water at constant speed, $U$, and constant angle of attack, then rapidly pulled out of the fluid in the spanwise direction. Viewed within a fixed plane perpendicular to the span, the cross-sectional area of the foil seemingly disappears. The rapid spanwise motion results in the nearly instantaneous shedding of the boundary layer into the surrounding fluid. Particle image velocimetry measurements show that the shed layers quickly transition from free shear layers to form two strong, unequal-strength vortices, formed within non-dimensional time ${t}^{\ensuremath{\ast} } = 0. 03$, based on the foil chord and forward velocity. These vortices are connected to, and interact with, the foil’s tip vortex through additional streamwise vorticity formed during the rapid pulling of the foil. Numerical simulations show that two strong spanwise vortices form from the shed vorticity of the boundary layer. The three-dimensional effects of the foil removal process are restricted to the tip of the foil. This method of vorticity transfer may be used for quickly introducing circulation to a fluid to provide forcing for biologically inspired flow control.
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Solař, Jaroslav. "Sizing the Thickness of the Coated Insulation against Methane Leakage Coming out of Bedrock." Applied Mechanics and Materials 501-504 (January 2014): 2327–30. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.2327.

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On the surface of the Earth, methan is usually located in undermined areas, especially in places where the mining was stopped already. The protection of buildings from methan coming out of bedrock can be provided by layer isolation made of suitable type of polymer foil. The entry deals with the matter of designing the isolation against penetrating methan coming out of bedrock into surface line buildings (e.g. shaft, reservoir, water tower etc.).
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McCormick, Michael E., and Luca Caracoglia. "Hydroelastic Instability of Low Aspect Ratio Control Surfaces." Journal of Offshore Mechanics and Arctic Engineering 126, no. 1 (February 1, 2004): 84–89. http://dx.doi.org/10.1115/1.1643084.

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As the operational speeds of surface ships and submarines increase, so does the probability that unwanted vibrations caused by the hydroelastic instability (flutter) of the special class of hydrofoils called control surfaces. These include rudders and diving planes. By nature, these are thick symmetric hydrofoils having low aspect ratios. The 3-D tip effects become more pronounced as the aspect ratio decreases. In the present study, the added-mass and circulation terms of the 2-D flutter equations are modified to include three-dimensional effects. The modifications are performed by introducing quasi-steady coefficients to each term. The results predicted by the modified equations are found to compare well with experimental results on a towed rectangular foil having an aspect ratio of one.
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Glauberman, M., A. Doroshenko, K. Shestopalov, K. Liudnytskyi, K. Zhuk, and A. Tsapushel. "Solar desiccant-evaporative cooling systems with ceramic packing (microporous multichannel structures)." Physics of Aerodisperse Systems, no. 54 (December 14, 2017): 66–82. http://dx.doi.org/10.18524/0367-1631.2017.54.132732.

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In this paper, a method for the determination of the efficiency and limitations of the evaporative cooling process is presented. Ceramic is employed as a packing material in the evaporative equipment. It is shown that the experimental efficiency of the ceramic packing is 10-20% higher as compared to packings made of aluminum foil and multichannel polycarbonate plates because of the absence of common liquid film on the packing surface, and due to the absolute wettability of the ceramic packing. Heat and mass transfer equipment for desiccant-evaporative cooling systems (direct and indirect evaporative coolers, cooling tower) utilizing ceramic structures has been developed.
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Zheng, Linhe, Zhilin Liu, Guosheng Li, ShouZheng Yuan, and Songbai Yang. "Experimental and numerical investigation on control strategies for heave and pitch motion reduction of a catamaran." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 235, no. 2 (February 20, 2021): 311–26. http://dx.doi.org/10.1177/1475090221993650.

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In this study, simulations and experiments were conducted on reducing the heave and pitch motions of a catamaran. To serve as stability appendages, an actively controlled T-foil and flap were designed, including their dimensions and installation position on the catamaran. Based on the uncoupled analysis of the appendages, the following control strategies were adopted: the previously proposed resultant force and moment distribution with feedback by displacement (RFMD-D) and the newly developed resultant force and moment distribution with feedback by velocity (RFMD-V). These two control strategies were applied to an S-plane controller, and their performances were tested in simulations and experiments. Finally, a bare catamaran and catamaran with actively controlled appendages were towed in a towing tank, and the two control strategies were tested. The results showed that both control strategies are effective and that RFMD-V is more effective than RFMD-D.
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XU, MAI, MARIA PETROU, and JIANHUA LU. "LEARNING LOGIC RULES FOR THE TOWER OF KNOWLEDGE USING MARKOV LOGIC NETWORKS." International Journal of Pattern Recognition and Artificial Intelligence 25, no. 06 (September 2011): 889–907. http://dx.doi.org/10.1142/s0218001411008610.

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In this paper, we propose a novel logic-rule learning approach for the Tower of Knowledge (ToK) architecture, based on Markov logic networks, for scene interpretation. This approach is in the spirit of the recently proposed Markov logic networks for machine learning. Its purpose is to learn the soft-constraint logic rules for labeling the components of a scene. In our approach, FOIL (First Order Inductive Learner) is applied to learn the logic rules for MLN and then gradient ascent search is utilized to compute weights attached to each rule for softening the rules. This approach also benefits from the architecture of ToK, in reasoning whether a component in a scene has the right characteristics in order to fulfil the functions a label implies, from the logic point of view. One significant advantage of the proposed approach, rather than the previous versions of ToK, is its automatic logic learning capability such that the manual insertion of logic rules is not necessary. Experiments of labeling the identified components in buildings, for building scene interpretation, illustrate the promise of this approach.
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Dissertations / Theses on the topic "Towed foils"

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Das, Anil P. V. "Propulsive Performance of Pitching Foils Investigated with Viscous Vortex Particle Method." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5289.

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Unsteady flapping foil based thrusters have emerged as ideal candidates for enabling propulsion in bioinspired and bio-mimetic devices such as autonomous underwater vehicles. To a large extent, this emergence has been driven by the extensive utilization of undulatory body motions in a wide spectrum of small to medium-sized swimming aquatic organisms. In the present work, the propulsive performance and related wake characteristics of both thrust generating towed foils and self-propelling pitching foils are investigated over a wide range of Reynolds numbers (Re) from 10 to 10,000. The effect of geometric and kinematic parameters like Strouhal number (St), amplitude of pitching and density ratio of the foil to fluid have been investigated from an energetic efficiency perspective. The above studies are performed using a high resolution two dimensional viscous vortex particle method (VVPM) based fluid structure interaction solver capable of handling both actively and passively moving bodies. The solver incorporates a new coupling algorithm for passively moving rigid bodies using vortex impulse. In order to reduce the time to solution of the solver, the implementation has been ported onto a graphics processing unit(GPU). For thrust producing towed foils, a sharp increase is observed in the peak energetic efficiency as Re is increased from 50 to 1000, with the efficiency values being nearly constant at higher Re values. The wake shows a variety of different regimes that are dependent on Re and St, and a wake map has been obtained in this two-dimensional parameter space. The map shows that the peak efficiency values at a given Re correspond to the region where the wake is asymmetric, while the von Karman to reverse von Karman wake transition precedes the drag-to-thrust transition at all Re. For thick foils, the number of wake regimes is found to substantially increase primarily due to the generation of a stronger leading edge vortex, which in turn interacts with the trailing edge vortex; this interaction being sensitive to the motion parameters of the pitching foil. An important characteristic of such propulsion systems is the St for the transition from drag to thrust at a given Re, with this value showing a very clear power law scaling with Re. This scaling relation can also be independently derived based on a balance between thrust produced from pitching motions and the viscous skin friction drag. At this transition condition, the net force is zero, and this corresponds to the case when the foil is self-propelling. For such selfpropelling cases, studies have been done with different degrees of freedom, which includes permitting only chordwise motion and the possibility of self-induced heaving motions during the pitching cycle. The average chordwise self-propelled motions of the pitching foil are found to be strongly dependent on the degrees of freedom. This work thus provides a comprehensive characterization of pitching foil based propulsion under both thrust producing towed and self-propelling conditions from both the energetic and the wake perspective.
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Books on the topic "Towed foils"

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Sapkowski, Andrzej. Tower of Fools. Orbit, 2020.

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Sapkowski, Andrzej. Tower of Fools. Orbit, 2020.

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Sapkowski, Andrzej. Tower of Fools. Orbit, 2020.

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Sapkowski, Andrzej. Tower of Fools. Orion Publishing Group, Limited, 2020.

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Blore, Erick. Tower of Fools. Eclectry Books, 2011.

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Sapkowski, Andrzej. Tower of Fools. Orion Publishing Group, Limited, 2020.

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Sapkowski, Andrzej. The Tower of Fools. Hachette B and Blackstone Publishing, 2020.

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Sapkowski, Andrzej. Tower of Fools: From the Bestselling Author of the WITCHER Series Comes a New Fantasy. Orion Publishing Group, Limited, 2021.

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Conference papers on the topic "Towed foils"

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Fernandez-Prats, R., and F. J. Huera-Huarte. "Hydrodynamic Forces and DPIV on a Towed Pitching Foil." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21465.

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More than 90% of the thrust generated by thunniform swimmers is known to be produced by the oscillation of their caudal fin, and the rest by their caudal peduncle. We have designed an experiment in which we can mimic, in a simplified manner, the kinematics of swimmers that mainly use their caudal fin for propulsion. The set-up consists of a rectangular foil attached to a shaft that is controlled by a stepper motor, and the whole assembly can be towed in still water at different controllable speeds. With this system we can study the effect of different types of pitching on the hydrodynamic loads and the performance of the propulsion system. By changing the type of foil, the effects of the flexibility in the propulsion can also be analysed. Hydrodynamic loads were measured with a 6-axes balance, and the flow structures were investigated using a Digital Particle Image Velocimetry (DPIV). Loads and DPIV velocity fields were acquired synchronously.
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Bruckner, Robert J. "An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22118.

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Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8–13% of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (∼25000 pound) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05%.
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Dubois, Marc. "Le Corbusier et la Belgique / Son Héritage." In LC2015 - Le Corbusier, 50 years later. Valencia: Universitat Politècnica València, 2015. http://dx.doi.org/10.4995/lc2015.2015.896.

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Résumé: À la suite de l’exposition de Paris 1925, le peintre René Guiette demande à LC de lui construire une maison avec atelier à Anvers. Ce bâtiment superbe existe encore, le seul témoignage de LC construit en Belgique! LC vient pour la première fois à Bruxelles en 1926 pour donner une conférence. Après une deuxième conférence en 1928 il reçoit une commande de Jean Canneel-Claes pour une maison, publiée par Le Corbusier en 1929 comme « Maison pour M. X à Bruxelles ». En 1930, il est présent à Bruxelles pour le congres CIAM. En 1933, LC participe au concours pour la Rive Gauche d’Anvers. En 1938 on lui demande de participer à l’ exposition de Liège en 1939, mais rien n’est construit. LC est présent à l’exposition Universelle de Bruxelles 1958 avec le pavillon exceptionnel pour Philips. Après l’expo, Le Poème Electronique est démoli. Keywords: LC 5xBelgique, Stynen & De Meyer, deSingel, Riverside Tower. DOI: http://dx.doi.org/10.4995/LC2015.2015.896
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Jovanova, Jovana, Maja Anachkova, Viktor Gavriloski, Dimitar Petrevski, Franka Grazhdani, and Damjan Pecioski. "Modular Origami Robot Inspired by a Scorpion Tail." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8177.

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Arthropod animals like scorpions with modular body parts can be an inspiration for a robot’s structure. The design presented here relays on inter-connected origami towers, but could also be easily disassembled. Each origami tower is fully autonomous and at the same time is part of the robot as a whole. The towers are positioned between two platforms that enable modularity. The scorpion’s tale shape is achieved by the varying platform diameter resulting in cone-like form. Each tower is actuated independently to enable multiple degrees of freedom. Maneuvering with separated units, assists in easier reparation as well as replacement. Detaching the towers into separate parts makes this structure develop more precise movements, since every unit will move autonomously. Therefore, having a higher number of separated movements combined leads to a smooth bionic movement. So, the overall hierarchy will be modular contributing to a greater curvature bending of the whole structure. Actuating and maneuvering the robot in the main concept is done by separated electro motors, built in the platform. The basic structure will be built from thick paper with plastic coatings. The thick paper itself is lightweight, but at the same time flexible. To protect the paper towers, double plastic foil is placed as an outer coating which acts as an origami cover. This transparent layer is elastic hence it can follow and support the individual units’ movements. This work is focused on understanding origami towers kinematics and different combinations of inter-connected towers to achieve multiple degrees of freedom. A conceptual model is developed, supported by CAD and mathematical models. At the end a prototype is presented.
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