2,220 research outputs found
Numerical Analysis of Damage Iinitiation and Development in Bends of Steel Pipelines
No full textGasses and fluids are transported via an extensive infrastructure of steel pipelines. In the design of pipeline systems the use of elbows (pipe bends) is important because their flexibility makes them able to sustain significant deformations. These bends can be subjected to permanent deformations due to various load combinations which can lead to progressive material damage. There are three stages commonly observed in ductile damage: void nucleation, growth and coalescence. When subjected to varying bending loads low cycle fatigue damage may occur. Within this research project Finite Element Analysis is used to simulate the response of pipeline bends. Two element types are implemented to model a pipe bend, the classical shell element and an efficient tube element (pipe elbow element), respectively. To predict the structural response when subjected to monotonic loading a damage model is implemented for both elements. When subjected to cyclic loading three phases can be identified. During the first few cycles the permanent deformation increases rapidly. After some cycles, the rate of permanent deformation stabilizes until the point of response degradation. In order to capture this response a new material model, based upon the afore mentioned model, is proposed. Experiments have indicated that this model is well suited to determine the point of material failure.Structural MechanicsCivil Engineering and Geoscience
Large scale wavefront reconstruction for the next generation of Extreme Large Scale Telescopes (E-ELT)
No full textThe spatial resolution of an astronomical telescope is limited by either by the diffraction of light and the amount of aberrations caused in the atmosphere. To increase the diffraction limited resolution, the size of telescopes increases such as the to be build European Extremely Large Telescope (E-ELT). To fully benefit from the increased diffraction limited resolution, also the ability of adaptive optics to compensate for the wavefront aberrations should increase. This is for example done by increase the number of spatial wavefront measurements. This demands algorithms that are computationally efficient and highly parallelizable. In this thesis it is discussed whether the recently introduced Spline based ABeration REconstruction (SABRE) method can be parallelized. It is discussed that SABRE can be solved with the null-space method, resulting in a system of equations similar to the Poisson equation. The Conjugate Gradient (CG) method with different preconditioners, namely the Approximate INVerse (AINV), Algebraic Multigrid (AMG) and Incomplete Cholesky factorization (ICHOL), are used that make use of the sparsity of SABRE are discussed, their scalability and parallelism seem to be promising but the high amount of communication lowers the expectations. Experiments on the Graphics Processing Unit (GPU) give results, that matches with these expectations. Although there is plenty of parallelism, the sparse solvers are limited by the communication and therefore, for the grid sizes discussed in this thesis, slower than their counter ones on the Central Processing Unit (CPU). But there is lot of optimization possible and especially the CG with the AINV has a lot of potential. Further research is required.Systems and ControlDelft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
CLASSICAL STUDIES:TO 155-TH ANNIVERSARY OF A.E. ALEKTOROV
No full textThe article, written in the genre of the response to read the book, devoted to the 155 anniversary since the birth of A. E. Alektorov. The author attempts to comprehend and describe the publishing and pedagogical activity of A.E. Alektorov for example, fundamental bibliographic work
Spline-based wavefront reconstruction for Shack-Hartmann measurements
No full textIn the coming decade, a new generation of extremely large-scale ground-based astronomical telescopes will see first light. It is well known that increasing the size of the telescope aperture is only beneficial if the adaptive optics (AO) system, which compensates for turbulence-induced wavefront aberrations, scales accordingly. For the extreme-AO (XAO) system of the future European Extremely Large Telescope (E-ELT), in the order of 10^4–10^5 unknown phase points have to be estimated at kHz range frequencies to update the actuator commands of the corrective device, consisting of a deformablemirror (DM).The work on fast algorithms for wavefront reconstruction (WFR) for real-time application has therefore been extensive. Conventional WFR algorithms estimate the unknown wavefront from wavefront sensor (WFS) measurements. They are generally based on a linear relationship between the unknown wavefront and the sensor read out, and assume one of the two following principles. Zonal methods represent the wavefront as discrete phase points in terms of which the sensor model is formulated, leading to a per se local phase-measurement relationship. The second group of modal methods expands the wavefront with a set of globally defined polynomials which results in a sensormodel that acts on the entire sensor domain.Team Raf Van de Pla
The A.E. Coppard Papers at Syracuse
No full textSome of the most choice collections in the Manuscript Department of Syracuse University Libraries are also among the most modest in extent. The papers of English author and poet A.E. Coppard fit into both categories. Housed comfortably in a single box, fifty-five letters, three short stories in holograph and one speech provide a close look at Coppard\u27s literary theories, criticism, opinions of his own work and that of a few others, reaction to approaches regarding dramatizing, filming or televising his prose works, dealings with publishers, and his activities on behalf of world peace through the Authors\u27 World Peace Appeal in the early 1950\u27s
Covariance matrix-based fire and flame detection method in video
No full textThis paper proposes a video-based fire detection
system which uses color, spatial and temporal information.
The system divides the video into spatio-temporal blocks and
uses covariance-based features extracted from these blocks
to detect fire. Feature vectors take advantage of both the spatial and the temporal characteristics of flame-colored regions. The extracted features are trained and tested using a support vector machine (SVM) classifier. The system does not use a background subtraction method to segment moving regions and can be used, to some extent, with non-stationary cameras. The computationally efficient method can process 320×240 video frames at around 20 frames per second in an ordinary PC with a dual core 2.2 GHz processor. In addition, it is shown to outperform a previous method in terms of detection performance
In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?
No full textQuasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and 20%. However, differences in the size and possibly the shape, but also in the fibre lay-up, between test coupons and components or structures raise additional questions: Is G from a coupon test a suitable parameter for describing the behaviour of delaminations in composite structures? Can planar, two-dimensional, delamination propagation in composite plates or shells be properly predicted from essentially one-dimensional propagation in coupons? How does fibre bridging in unidirectionally reinforced test coupons relate to delamination propagation in multidirectional lay-ups of components and structures? How can multiple, localised delaminations—often created by impact in composite structures—and their interaction under service loads with constant or variable amplitudes be accounted for? Does planar delamination propagation depend on laminate thickness, thickness variation or the overall shape of the structure? How does exposure to different, variable service environments affect delamination initiation and propagation? Is the microscopic and mesoscopic morphology of FRP composite structures sufficiently understood for accurate predictive modelling and simulation of delamination behaviour? This contribution will examine selected issues and discuss the consequences for test development and analysis. The discussion indicates that current coupon testing and analysis are unlikely to provide the data for reliable long-term predictions of delamination behaviour in FRP composite structures. The attempts to make the building block design methodology for composite structures more efficient via combinations of experiments and related modelling look promising, but models require input data with low scatter and, even more importantly, insight into the physics of the microscopic damage processes yielding delamination initiation and propagation.</p
The Ethical Economy of Customer Coproduction
No full textIn this article, the author argues that customer coproduction should be understood as an expression of a large-scale trend toward the increasing power and relevance of social production. Social production consists in the self-organized systems of (mostly immaterial) production that have evolved around the diffusion of networked information and communication tech-nologies. An analysis of the genealogy of social production is shared; this includes tracing it to the process of re-mediation of social relations put in motion by the expansion of the capitalist economy into the fields of culture and consciousness and the concomitant socialization of production relations. The author then argues that social production, including customer coproduction, follows a very particular economic logic—that is, an ethical economy where value is related to social impact rather than monetary accumulation. A detailed analysis of the logic of this ethical economy is offered; it draws out some implications for the successful management of ever more customer-centric brands, whereby the consumers are directly involved in the processes that add value
GPU implementation for spline-based wavefront reconstruction
No full textThis paper presents an adaptation of the distributed-spline-based aberration reconstruction method for Shack–Hartmann (SH) slope measurements to extremely large-scale adaptive optics systems and the execution on graphics processing units (GPUs). The introduction of a hierarchical multi-level scheme for the elimination of piston offsets between the locally computed wavefront (WF) estimates solves the piston error propagation observed for a large number of partitions with the original version. To obtain a fully distributed method for WF correction, the projection of the phase estimates is locally approximated and applied in a distributed fashion, providing stable results for low and medium actuator coupling. An implementation of the method with the parallel computing platform CUDA exploits the inherently distributed nature of the algorithm. With a standard off-the-shelf GPU, the computation of the adaptive optics correction updates is accomplished in under 1 ms for the benchmark case of a 200×200 SH array.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.Team Raf Van de PlasControl & SimulationNumerical Analysi
Prefazione [a: Michail Kuzmin, Le stagioni dell'amore, Bari, Stilo, 2020, 172 pp.]
No full text"Kuranty ljubvi" (Le stagioni dell'amore) è un piccolo, ma poeticamente significativo, contributo alla produzione letteraria del Simbolismo russo nel segno della sintesi delle arti. Michail Kuzmin, uno dei più importanti scrittori di quell'epoca, è l'autore del ciclo poetico-musicale e delle partiture."Kuranty ljubvi" (The seasons of love) is a small but poetically significant contribution to the literary production of Russian Symbolism in the context of the synthesis of the arts. Michail Kuzmin, one of the most important writers of that era, is the author of the poetic-musical cycle and of the scores
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