Готові списки джерел за темами / SPARS

Добірка наукової літератури з теми "SPARS"

Автор: Grafiati
Опубліковано: 11 вересня 2023

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Статті в журналах з теми "SPARS"

1

Rosenzweig, Michael L. "Reconciliation ecology and the future of species diversity." Oryx 37, no. 2 (April 2003): 194–205. http://dx.doi.org/10.1017/s0030605303000371.

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Species-area relationships (SPARs) dictate a sea change in the strategies of biodiversity conservation. SPARs exist at three ecological scales: Sample-area SPARs (a larger area within a biogeographical province will tend to include more habitat types, and thus more species, than a smaller one), Archipelagic SPARs (the islands of an archipelago show SPARs that combine the habitat-sampling process with the problem of dispersal to an island), and Interprovincial SPARs (other things being equal, the speciation rates of larger biogeographical provinces are higher and their extinction rates are lower, leading to diversities in proportion to provincial area). SPARs are the products of steady-state dynamics in diversity, and such dynamics appears to have characterized the earth for most of the last 500 million years. As people reduce the area available to wild species, they impose a linear reduction of the earth's species diversity that will follow the largest of these scales, i.e. each 1% reduction of natural area will cost about 1% of steady-state diversity. Reserving small tracts of wild habitat can only delay these reductions. But we can stop most of them by redesigning anthropogenic habitats so that their use is compatible with use by a broad array of other species. That is reconciliation ecology. Many pilot projects, whether intentionally or inadvertently espousing reconciliation ecology, are demonstrating that it can be done.
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2

Alex Tullo. "Braskem spars with Pemex." C&EN Global Enterprise 98, no. 47 (December 7, 2020): 10. http://dx.doi.org/10.1021/cen-09847-buscon6.

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3

ENNOS, A. ROLAND. "The Importance of Torsion in the Design of Insect Wings." Journal of Experimental Biology 140, no. 1 (November 1, 1988): 137–60. http://dx.doi.org/10.1242/jeb.140.1.137.

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A model insect wing is described in which spars of corrugated membrane which incorporate stiffening veins branch serially from a V-section leading edge spar. The mechanical behaviour of this model is analysed. The open, corrugated spars possess great resistance to bending, but are compliant in torsion. Torsion of the leading edge spar will result in torsion and relative movement of the rear spars. As a result camber will automatically be set up in the wing as it twists. Aerodynamic forces produced during the wing strokes will result in torsion and camber of the wing which should improve its aerodynamic efficiency. The effects of varying parameters of the wing model are examined. For given wing torsion, higher camber is given by spars branching from the leading edge at a lower angle, by spars which curve posteriorly, and by spars which diverge from each other. Wings of three species of flies were each subjected to two series of mechanical tests. Application of a force behind the torsional axis caused the wings to twist and to develop camber. Immobilizing basal regions of the leading edge greatly reduced compliance to torsion and camber, as predicted by the theoretical model. Aerodynamic forces produced during a half-stroke are sufficient to produce observed values of torsion and camber, and to maintain changes in pitch caused by inertial effects at stroke reversal.
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4

Hayat, Khazar, Shafaqat Siddique, Tipu Sultan, Hafiz T. Ali, Fahed A. Aloufi, and Riyadh F. Halawani. "Effect of Spar Design Optimization on the Mass and Cost of a Large-Scale Composite Wind Turbine Blade." Energies 15, no. 15 (August 2, 2022): 5612. http://dx.doi.org/10.3390/en15155612.

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Mass and cost tradeoffs by deploying three optimized spars, made of all-glass, hybrid and all-carbon composites, applied to a publicly available large-scale composite blade of 100 m in length for a 13.2 MW wind turbine, are explored. The blade mass and cost minimizations are calculated for two design load cases, generating the worst aerodynamic loads for parked and rotating rotor blades, while meeting the stiffness, strength, stability and resonance design requirements, as recommended by the wind turbine standards. The optimization cases are formulated as a single-objective, multi-constraint optimization problem, while taking into account the manufacturability of hybrid spars in particular, and it is solved using a genetic algorithm method. The blade mass lowers in the range of 8.1–13.3%, 18.5–20.7% and 25.7–26.4% for the optimized all-glass, hybrid and all-carbon spars, respectively, while the cost decreases for the optimized all-glass spars only. The cost increases in a range of 1.2–13.6% and 24.5–31.5% when the optimized hybrid and all-carbon spars are used. Further, the hybrid spar optimization using the blade mass and cost objective functions, as well as the effects of spar optimization on the blade’s structural performance in terms of tip deflection, strength, buckling resistance and first natural frequency, are discussed.
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5

Qasim, Isa C. "Navigating the Trunks and Spars." New Criminal Law Review 24, no. 4 (2021): 518–67. http://dx.doi.org/10.1525/nclr.2021.24.4.518.

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In 2018, the Supreme Court issued a little noticed decision, Currier v. Virginia, that signaled a potential revolution in the Double Jeopardy Clause doctrine. This essay uses that decision to reconsider the Clause’s disparate protections, seeking coherence in this long-confused area of law. In doing so, it finds that the central protections of the Clause are best understood through a single, novel framework: the jury-preservation theory of double jeopardy. This essay explicates the theory, explaining its roots in the Revolutionary Era jury, its applications to modern double jeopardy law, and its implications for Currier and future double jeopardy cases.
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6

Finn, L. "Reliable Riser Systems for Spars." Journal of Offshore Mechanics and Arctic Engineering 121, no. 4 (November 1, 1999): 201–6. http://dx.doi.org/10.1115/1.2829568.

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The Spar concept as a floating vessel is now recognized as a reliable and economic option for developing deepwater offshore hydrocarbon reservoirs. Many of the advantages of the Spar concept are attributed to the variety of riser systems that can be accommodated. This paper presents a discussion of design considerations for the top tensioned and steel catenary risers deployed from a Spar offshore production vessel. Results from extreme event strength analysis, Spar motion and current-induced fatigue analysis, and a riser-to-riser wake interference analysis are presented. Steel catenary risers are presented, including a comparison of results for risers supported by a Spar and a Semi. These analyses demonstrate that simple and reliable riser systems can be designed for use with the Spar platform concept.
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7

Bramesfeld, Götz, and Ryan Prinster. "Design and testing of foam-inflated wings for small unmanned aerial vehicles." Journal of Unmanned Vehicle Systems 3, no. 4 (December 1, 2015): 176–91. http://dx.doi.org/10.1139/juvs-2014-0018.

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Inflatable wings can greatly improve the portability of small UAVs. The foam-inflated wing concept consists of a hybrid structure of rigid and flexible elements. This approach potentially reduces the packaging and logistical needs before deployment of a small UAV. The small packaging volume of the wing is achieved using spars and wing skin that are made out of flexible polyester-film material. For deployment, the cylindrical spars are rigidized using expanding foam that increases the buckling stiffness of the spars. Solid ribs that were previously attached to those spars provide high shape compliance for the external skin. Due to the solid rib structure, the chord length of the wing defines the maximum packing dimension before inflation. As demonstrated in tests, the inflation process of the hybrid wing is uncomplicated and swift. The subsequent foam-inflated structure is lightweight and can be tailored to the expected loads. In addition, the underlying ribs ensure a high aerodynamic quality, despite the inflatable nature of the hybrid wing structure. The feasibility of the concept of the hybrid wing structure has been demonstrated in flight tests.
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8

Vogel, G. "EDUCATION: California Spars Over Math Reform." Science 277, no. 5330 (August 29, 1997): 1194. http://dx.doi.org/10.1126/science.277.5330.1194.

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9

Perlman, Lisa. "Rocket spars as science is attacked." Nature 344, no. 6267 (April 1990): 578. http://dx.doi.org/10.1038/344578c0.

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Scholl, Bernd. "Klebstoffe geben Gas — schnell, zuverlässig, spars." adhäsion KLEBEN & DICHTEN 61, no. 12 (December 2017): 30–33. http://dx.doi.org/10.1007/s35145-017-0094-7.

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Дисертації з теми "SPARS"

1

Rashid, Adnan. "Investigation of through-thickness assembly stresses in composite wing spars." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.722699.

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2

Mehler, Felix Eckhart. "The structural testing and modification of a full-scale ornithopter's wing spars." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29368.pdf.

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3

Blondeau, Julie E. "Development and testing of a variable aspect ratio wing using pneumatic telescopic spars." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1761.

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Thesis (M.S.) -- University of Maryland, College Park, 2004.
Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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4

De, Shuvodeep. "Structural Modeling and Optimization of Aircraft Wings having Curvilinear Spars and Ribs (SpaRibs)." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/88467.

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The aviation industry is growing at a steady rate but presently, the industry is highly dependent on fossil fuel. As the world is running out of fossil fuels and the wide-spread acceptance of climate change due to carbon emissions, both the governments and industry are spending a significant amount of resources on research to reduce the weight and hence the fuel consumption of commercial aircraft. A commercial fixed-wing aircraft wing consists of spars which are beams running in span-wise direction, carrying the flight loads and ribs which are panels with holes attached to the spars to preserve the outer airfoil shape of the wing. Kapania et al. at Virginia Tech proposed the concept of reducing the weight of aircraft wing using unconventional design of the internal structure consisting of curvilinear spars and ribs (known as SpaRibs) for enhanced performance. A research code, EBF3GLWingOpt, was developed by the Kapania Group. at Virginia Tech to find the best configuration of SpaRibs in terms of weight saving for given flight conditions. However, this software had a number of limitations and it can only create and analyze limited number of SpaRibs configurations. In this work, the limitations of the EBF3GLWingOpt code has been identified and new algorithms have been developed to make is robust and analyze larger number of SpaRibs configurations. The code also has the capability to create cut-outs in the SpaRibs for passage of fuel pipes and wirings. This new version of the code can be used to find best SpaRibs configuration for multiple objectives such as reduction of weight and increase flutter velocity. The code is developed in Python language and it has parallel computational capabilities. The wing is modeled using commercial FEA software, MSC.PATRAN and analyzed using MSC.NASTRAN which are from within EBF3GLWingOpt. Using this code a significant weight reduction for a transport aircraft wing has been achieved.
PHD
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5

Carlowitz, Christian, Thomas Girg, Hatem Ghaleb, and Xuan-Quang Du. "Efficient Ultra-High Speed Communication with Simultaneous Phase and Amplitude Regenerative Sampling (SPARS)." De Gruyter, 2017. https://tud.qucosa.de/id/qucosa%3A38596.

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For ultra-high speed communication systems at high center frequencies above 100 GHz, we propose a disruptive change in system architecture to address major issues regarding amplifier chains with a large number of amplifier stages. They cause a high noise figure and high power consumption when operating close to the frequency limits of the underlying semiconductor technologies. Instead of scaling a classic homodyne transceiver system, we employ repeated amplification in single-stage amplifiers through positive feedback as well as synthesizer-free self-mixing demodulation at the receiver to simplify the system architecture notably. Since the amplitude and phase information for the emerging oscillation is defined by the input signal and the oscillator is only turned on for a very short time, it can be left unstabilized and thus come without a PLL. As soon as gain is no longer the most prominent issue, relaxed requirements for all the other major components allow reconsidering their implementation concepts to achieve further improvements compared to classic systems. This paper provides the first comprehensive overview of all major design aspects that need to be addressed upon realizing a SPARS-based transceiver. At system level, we show how to achieve high data rates and a noise performance comparable to classic systems, backed by scaled demonstrator experiments. Regarding the transmitter, design considerations for efficient quadrature modulation are discussed. For the frontend components that replace PA and LNA amplifier chains, implementation techniques for regenerative sampling circuits based on super-regenerative oscillators are presented. Finally, an analog-to-digital converter with outstanding performance and complete interfaces both to the analog baseband as well as to the digital side completes the set of building blocks for efficient ultra-high speed communication.
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6

Wynn, Milton E. "Spare parts nonavailability : the identification of impediments to spares acquisition." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24042.

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7

Sohaib, Muhammad. "Parameterized Automated Generic Model for Aircraft Wing Structural Design and Mesh Generation for Finite Element Analysis." Thesis, Linköpings universitet, Maskinkonstruktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-71264.

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This master thesis work presents the development of a parameterized automated generic model for the structural design of an aircraft wing. Furthermore, in order to perform finite element analysis on the aircraft wing geometry, the process of finite element mesh generation is automated. Aircraft conceptual design is inherently a multi-disciplinary design process which involves a large number of disciplines and expertise. In this thesis work, it is investigated how high-end CAD software‟s can be used in the early stages of an aircraft design process, especially for the design of an aircraft wing and its structural entities wing spars and wing ribs. The generic model that is developed in this regard is able to automate the process of creation and modification of the aircraft wing geometry based on a series of parameters which define the geometrical characteristics of wing panels, wing spars and wing ribs.Two different approaches are used for the creation of the generic model of an aircraft wing which are “Knowledge Pattern” and “PowerCopy with Visual Basic Scripting” using the CATIA V5 software. A performance comparison of the generic wing model based on these two approaches is also performed. In the early stages of the aircraft design process, an estimate of the structural characteristic of the aircraft wing is desirable for which a surface structural analysis (using 2D mesh elements) is more suitable. In this regard, the process of finite element mesh generation for the generic wing model is automated. The finite element mesh is generated for the wing panels, wing spars and wing ribs. Furthermore, the finite element mesh is updated based on any changes in geometry and the shape of the wing panels, wing spars or wing ribs, and ensure that all the mesh elements are always properly connected at the nodes. The automated FE mesh generated can be used for performing the structural analysis on an aircraft wing.
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8

Cox-Richard, Lillian. "Spark Gap." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/698.

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"Spark Gap" is an invisible electrical force made visible in spaces between things. This usually describes the space of air between two conductors; a non-conductive gap in an otherwise complete electric circuit, across which a quick luminous disruptive electrical discharge occurs. This interstitial space is the distance between two ideas, arced with a running leap. The arc can also be the difference between two things, a gap that becomes apparent only when the two are held in close proximity. In my thesis exhibition, "Spark Gap," a sea urchin shaped orb sits atop a tower of ladders. The orb is broken into five sections and reassembled, each fault line occurring along the perfect zigzag line of its cellular structure. On the floor, there is a linen shag rug, marked as if struck by lightning. This exhibition is named for an interstitial charge, arcing across distance or difference. But this charge is also found in intersections and similarities. Imagine the friction created by rubbing together the circles of a Venn diagram: the overlapping section would begin to spark. It is in these gaps and overlaps that I find the impetus for my work.
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9

Lustig, Michael. "Sparse MRI /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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10

Lowas, Albert Frank III. "Improved Spare Part Forecasting for Low Quantity Parts with Low and Increasing Failure Rates." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1432380369.

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Книги з теми "SPARS"

1

Farber, Thomas. Foregone conclusions: Equivoques, aperc̦us, spars & catarrhs. Berkeley, CA: Andrea Young Arts, 2011.

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2

Murphy, John McLeod. Spars and rigging from Nautical routine, 1849. Mineola, N.Y: Dover Publications, 2003.

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3

Sheahan, Matthew. Sailing rigs and spars: Installation, maintenance, tuning. Sparkford, Yeovil, Somerset, England: Haynes Pub. Group, 1990.

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4

Mehler, Felix Eckhart. The structural testing and modification of a full-scale ornithopter's wing spars. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1999.

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5

Mehler, Felix Eckhart. The structural testing and modification of a full-scale ornithopter's wing spars. [Toronto]: Dept. of Aerospace Science and engineering, University of Toronto, 1997.

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6

1957-, Izadpanah Amir P., Baucom Robert M, and United States. National Aeronautics and Space Administration. Scientific and Technical Information Program., eds. Experimental and analytical investigation of dynamic characteristics of extension-twiet-coupled composite tubular spars. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, 1993.

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7

Lake, Renee C. Experimental and analytical investigation of dynamic characteristics of extension-twist-coupled composite tubular spars. Hampton, Va: Langley Research Center, 1993.

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8

Ryburn, Wayne. Tall spars, steamers & gum: A history of the Kaipara from early European settlement, 1854-1947. Auckland, N.Z: Kaipara Publications, 1999.

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9

Wynn, Milton E. Spare parts nonavailability: The identification of impediments to spares acquisition. Monterey, Calif: Naval Postgraduate School, 1992.

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10

Spark. Sydney, N.S.W: [publisher not identified], 2014.

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Частини книг з теми "SPARS"

1

Samset, Ivar. "Anchors, Spars and Intermediate Supports." In Winch and cable systems, 97–116. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-017-3684-8_8.

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2

Wu, Shukai. "Taut-Leg Mooring System and Anchoring for Spars." In Spar Platforms, 33–77. Reston, VA: American Society of Civil Engineers, 2012. http://dx.doi.org/10.1061/9780784412091.ch02.

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3

Schneider, T., and E. Henze. "The Monolithic CFRP-Substructure with Corrugated V-Spars an Alternative to Sandwich Constructions." In Developments in the Science and Technology of Composite Materials, 857–63. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0787-4_121.

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4

Weber, D., B. Kirsch, C. R. D‘Elia, B. S. Linke, M. R. Hill, and J. C. Aurich. "Simulation-Based Investigation of the Distortion of Milled Thin-Walled Aluminum Structural Parts Due to Residual Stresses." In Proceedings of the 3rd Conference on Physical Modeling for Virtual Manufacturing Systems and Processes, 149–69. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-35779-4_9.

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AbstractNowadays, aluminum components in aircraft are mainly found in the form of thin-walled monolithic structural parts of the internal fuselage and the wings as spars and ribs [1]. This is because these components have excellent material properties for lightweight applications, such as a high strength-to-weight ratio and good corrosion resistance [2]. A typical manufacturing process to produce such structural components is milling. For these weight-optimized, monolithic components, up to 95% of the material is removed by machining [3]. The challenge with these thin-walled structural components, which are up to 14 m long, is that part distortion can occur because of the manufacturing-specific process chain [4]. Residual stresses due to machining and upstream processes such as forming, and heat-treatments are known to be the key factor for causing those distortions [5].In this research the effect of the residual stresses, the machining strategy, the part topology and the geometry, including the wall-thickness, on distortion were investigated experimentally, and simulatively by validated virtual models based on the finite-element method. Those models can then be used to predict the distortion. At the end distortion minimization techniques were derived.
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Wang, Bo, Sheng Ma, Yuan Yuan, Yi Dai, Wei Jiang, Xiang Hou, Xiao Yi, and Rui Xu. "SparG: A Sparse GEMM Accelerator for Deep Learning Applications." In Algorithms and Architectures for Parallel Processing, 529–47. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-22677-9_28.

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Page, Norman. "A Writer’s Life." In Muriel Spark, 1–9. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-20716-9_1.

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Page, Norman. "Angels Dining at the Ritz: The Early Novels." In Muriel Spark, 10–53. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-20716-9_2.

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Page, Norman. "Interlude." In Muriel Spark, 54–63. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-20716-9_3.

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Page, Norman. "Foreign Parts: The Later Novels." In Muriel Spark, 64–110. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-20716-9_4.

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Page, Norman. "Back to the Fifties." In Muriel Spark, 111–15. London: Macmillan Education UK, 1990. http://dx.doi.org/10.1007/978-1-349-20716-9_5.

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Тези доповідей конференцій з теми "SPARS"

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Luo, Michael Y. H., Bob L. X. Zhang, Sudhakar Tallavajhula, and Sanjay Srinivasan. "Integrated Structural Analysis Methodology for Truss Spars." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29419.

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Eleven truss spars have been successfully installed in the deep water fields since late 2001. Compared with other floating systems, Truss spars offer significant advantages in motions, stability, and project schedule. One of the unique aspects of a truss spar is that it exhibits both high-frequency and low-frequency motion responses. The high-frequency motions, or wave frequency motions, are peaked around the wave spectral energy, while the low-frequency motions correspond to the natural periods of the spar’s rigid-body motions. Accurate structural design should include loads due to both wave and low frequency motions. The wave-frequency motions can be accurately estimated with potential/diffraction theory, but the low-frequency motions cannot be accounted for using the traditional spectral method. The traditional spectral method may be acceptable to other types of platforms such as Semi-submersibles and TLPs, but can become non-conservative for a spar structure. In the past, this challenge was overcome by performing time domain analysis to design the truss and a combined time and frequency domain analysis to design the other structural components. The procedure proved to be time consuming and inefficient, requiring extensive engineering hours. The hull design process was enhanced by developing an integrated structural analysis methodology. The methodology significantly reduces engineering hours and maintains accuracy in the estimation of loads by a combination of the wave frequency and low frequency motion responses. Efficient use of personnel for the labor-intensive structural modeling tasks was also achieved. Use of this methodology in two spar projects has proved to add significant value. The procedure is also applicable to a range of floating platforms such as Technip’s extended draft platform (EDP) and other deep draft floating platforms. Salient features of the integrated structural analysis methodology for both strength and fatigue analysis of the truss spar are discussed in the paper. Structural loads determined from the integrated methodology are compared with those from a complete time-domain analysis of the truss spar.
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Edelson, David, John Halkyard, Liyong Chen, and Luc Chabot. "Floatover Deck Installation on Spars." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29640.

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Анотація:
Deck installation is always a major installation challenge for floating structures, particularly deep draft floaters like the spar which must be installed in relatively deep water. Derrick barges have been used for spar deck installations until now. The 4000 mt deck for the Kikeh Spar was successfully installed using the floatover method in November 2006, off the coast of Sabah in the South China Sea. This demonstrates the feasibility of this concept and opens the door for more floatover decks on spars in the future. This paper will review the technical challenges associated with this type of installation. In particular, the authors will review past studies, which included analysis and model testing of similar deck floatovers for decks up to 30,000 t, and the analysis methods use to validate the procedures and equipment which was successfully used on the Kikeh project. The requirements for application of this technology in the Gulf of Mexico will be highlighted.
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3

Korpus, Richard, and Stergios Liapis. "Active and Passive Control of Spar Vortex-Induced Motions." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67245.

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Despite designer’s best efforts, Vortex-Induced Motion (VIM) of spars remains a significant problem. While strakes have proven highly effective at suppressing riser VIM, all three straked classical spars in the Gulf of Mexico continue to experience occasional VIM events. Since VIM can cause riser damage, mooring line fatigue, and even work stoppage, its suppression is a major priority. But designers will only successfully eliminate VIM once reliable predictions tools become available. VIM is both roughness and Reynolds number dependent, and spars lie outside the validated range of current computational tools in both these areas. This paper presents the development of Reynolds-Averaged Navier-Stokes (RANS) methods to predict real-world spar VIM behavior. It includes the ability to address rough surfaces and high super-critical Reynolds numbers. Validation is provided against existing experimental data where available. The resulting algorithms were used to assess effectiveness of two alternative control strategies for suppressing spar VIM. The first strategy consists of actively injecting fluid in a direction tangential to the spar. The second strategy is passive, and relies on adding an external sleeve to the spar. Active injection was found highly effective, and even capable of totally eliminating VIM. The passive alternative was also found to reduce VIM, but is not as effective as active injection.
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4

Shi, Shan, Charlie Mao, Jenny Yang, and Nishu Kurup. "New Design Configuration of Steel Catenary Risers With Pull-Tube for Spars." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-50303.

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In previous Spar designs where pull tubes were used to board the risers (either export or flowline risers), the pull-tube extended a considerable distance beyond the keel and used a tapered design to form a bend restrictor that supported the riser throughout the riser/hull interface. In a current Spar design, the pull-tube is terminated at the hull keel and the bending loads are carried by a double sided stress-joint in the riser that pivots on a centralizer located near the bottom of the pull-tube. Essentially, this is an adaptation of the double-sided stress joint used for top tensioned risers exiting the bottom of their buoyancy can stems to the similar condition of an SCR exiting a pull tube terminating at the Spar’s keel. This new pull-tube and SCR configuration can be applied for both Truss and Classic Spars. SCRs boarding Spars through pull tubes have several advantages over stress joints or flex-joints anchored in porches, notably, eliminating both the need for divers to make large piping connections at 500′ to 600′ water depths and the possibility of those connections leaking over time. Moving the bend restrictor function from the pull tube to the riser provides the additional advantage of adding flexibility for the Spar to accommodate future risers whose size and weight are not known at the time the pull tubes are designed and the platform is installed. With the stress joint as part of the riser, the bend restrictor can be custom designed for each riser since the pull tube works the same for all risers. The SCR and stress joint, pull-in and in-place analyses have been performed by using the finite element program ABAQUS. The nonlinear capabilities of ABAQUS including the hybrid, gap and contact element formulations are utilized in the analysis of the pull-in process. The nonlinear contact elements with finite sliding capability are modeled with an exponential over-closure relationship.
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5

Rodríguez, Claudio A., and Marcelo A. S. Neves. "Nonlinear Instabilities of Spar Platforms in Waves." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83577.

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Spars are widely recognized as an excellent choice for deep water applications due to their hydrodynamic characteristics. However, some relatively recent works report the occurrence of large motions in the plane perpendicular to wave incidence direction, i.e., not directly excited by waves. These unstable motions have been attributed to Mathieu instabilities, caused by pure hydrostatic variations of the underwater hull geometry. Based on a new approach developed by the Authors for predicting parametric rolling in ships, this nonlinear phenomenon has been investigated for spar platforms. The proposed approach demonstrates analytical and numerically that unstable motions, in fact, may appear, but the mechanism that triggers parametric rolling is not related to variations in the hull hydrostatic characteristics. Nonlinear pressure variations induced by waves passing along the spar introduce parametric excitation. Different from typical ship forms, where this effect is negligible even in very long waves due to shorter draughts, in spars, this excitation can be significant, especially for very long waves. The present paper presents the analytical expressions for roll parametric excitation in spars and numerically explores the proposed approach applied to a typical spar under a wide range of wave heights and periods. Parametric Amplification Domains (PADs) were numerically computed, showing not only the boundaries of the instability regions but also the maximum roll amplitudes.
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6

Murray, John, Edmund Muehlner, and Guibog Choi. "A Comparison of Radial Wellbay and Traditional Truss Spar Designs." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49272.

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The Spar continues to be a popular drilling and production platform design for ultra-deep water. In recent years, developers have introduced a number of design variations such as the Arctic Spar, closed centerwell Spar, and long Spar. As the industry moves production into ultra-deep water, the escalation in drilling costs, particularly for deeper more complicated wells, prompts the need to look for new deepwater floater designs, including Spars. This paper introduces some new features to the Truss Spar, including a radial wellbay layout and an adjustable buoyancy centerwell device. This new Radial Wellbay Spar design is investigated and compared to the traditional Truss Spar for the same topside and riser weights and subjected to the same environments. The base case assumes a drilling and production platform with the performance comparison made in terms of hull weights and dimensions and hull motions for post-Katrina Gulf of Mexico conditions. In general, the Radial Wellbay Spar offers a smaller hull with fewer mooring lines for the same payload while maintaining the Spar’s low motion performance.
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7

de Guzmán, Santiago, Daniel Marón, Pedro Bueno, Miguel Taboada, and Manuel Moreu. "A Reduced Draft Spar Concept for Large Offshore Wind Turbines." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77787.

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This paper describes a new floater type: the Reduced Draft Spar (RDS). The RDS is in essence a spar, and so stability in operation is achieved by having the center of gravity below the center of buoyancy. Spars thus need a relevant draft and some ballast at their bottom. The RDS instead, and compared to classic spars, increases the mass below the center of buoyancy to substantially reduce the draft. This counter-intuitive approach considerably increases the overall mass of the solution. But fortunately this additional mass can be provided by cost-effective solid ballast. In the same way gravity-based structures weigh much more than jackets or monopiles yet they can still be economically feasible, the RDS is considerably heavier than classic spars. Thereby, the RDS can have the benefits of reduced draft solutions like semis while keeping the inherent simplicity of spars. The RDS concept replaces the main cylinder of classic spars by a shorter one, which is in turn held by a large caisson at the bottom of the floater. This allows the assembly of the Wind Turbine (WT) onshore and gives to the RDS enough floating stability to perform the Transport and Installation (T&I) marine operations with a significant reduction of auxiliary means. The proposed floater is made of concrete. It supports an 8 MW turbine in a generic North Sea offshore location. Besides and like in some semis, the unit is fitted with an Active Ballast System (ABS) used to compensate the environmental mean loads (mainly the WT mean thrust). In the paper, a parametric design process is used to obtain the platform main dimensions. The intact stability, both in operation and during all marine operations phases, is checked taking into consideration reasonable design margins. The dynamic response of the RDS to extreme wind, waves and currents is also analyzed. A state-of-the-art seakeeping program coupled with a simplified aerodynamic load model accounts for the effect produced by the wind dynamics on the unit response. The performance of the platform in operation is similar to that of classic spars. Therefore, the paper focuses on the study of the survival conditions. Since the platform cross section is high, survival current loads become differentiating. The dynamic loads at the mooring lines are thus analyzed to assess their feasibility in severe storm environmental conditions, which rule over the mooring design.
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8

Gupta, Himanshu, Robert Blevins, and Hugh Banon. "Effect of Moonpool Hydrodynamics on Spar Heave." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57264.

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A Spar is a deep draft platform for oil and gas production and drilling operations. One of the features of the Spar platform is the presence of a moonpool (or centerwell) inside the cylindrical hull structure. A unique aspect of the moonpool in Spars is the presence of partial closure plates at the bottom. The seawater goes in and out of the moonpool though these bottom closure (or guide) plates. Depending on the design of a Spar (e.g., the number of risers), typical period of moonpool vertical oscillation can be close to the peak of extreme seastate spectra. The Spar heave motion is thus coupled with the moonpool water oscillation and presents itself as a two oscillator problem. The complex behavior of moonpool and Spar heave interaction is largely ignored in current practice, via conservative assumptions (this is also due to lack of a mathematical model). A new model describing this interaction between moonpool water oscillation and the Spar heave has been developed in this paper. The results of the new model highlight the importance of the moonpool hydrodynamics in predicting the heave motions of Spars.
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9

Chang, S. H. Mark, Yongming Cheng, Malcolm Vass, and Vincent Ledoux. "Hybrid Catenary Riser for Spar Application." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57064.

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Porches or pull tubes are typically used as conventional hang-off systems for catenary risers suspended from spars. The Hybrid Catenary Riser (HCR) is a novel hang-off alternative to suspend risers from spars where conventional hang-off systems are not available. The HCR consists of a section of flexible pipe suspended from the spar deck and running down to a location about 120 ft below the keel, where it is connected to regular Steel Catenary Riser (SCR) pipe. The flexible pipe passes through intermediate guides in the spar structure, a receptacle protruding from the spar keel, a curved guide pipe attached to the receptacle, and exits a bend stiffener attached to the curved pipe. The curved guide pipe controls the riser departure angle. During pull-in, a bend stiffener connector (BSC) will lock the bend stiffener to the curved pipe while the flexible pipe slides freely through the bend stiffener allowing the pipe to be pulled up to the spar deck. Feasibility of the HCR configuration is verified through state-of-the-art computer modeling. Installation procedures are developed to demonstrate installability. This paper presents the concept in detail and identifies its technical and economic advantages.
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10

Calogero, Joseph, Mary Frecker, Zohaib Hasnain, and James E. Hubbard. "Experimental Validation of Compliant Joints in a Dynamic Spar Numerical Model." In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9074.

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A dynamic spar numerical model for passive shape change is validated for a single degree of freedom contact-aided compliant mechanism (CCM) in a flapping spar. CCMs are modeled as compliant joints: spherical joints with distributed mass and three axis nonlinear torsional spring-dampers. Several assumptions were made in the original formulation of the model, such as assuming the spars were rigid and a simple damping model for the compliant joints. An experiment was performed to validate the assumptions and tune the model. Four configurations of the leading edge spar were tested: a solid spar, a previously designed CCM at two spatial locations, and a modified version of the CCM. Reflective markers were placed on each configuration, then the spars were inserted into the wing roots of a clamped ornithopter. An array of computer vision cameras was used to track the spar and CCM kinematics as they were flapped. First, a flapping angle function was extracted using a moving average of the flapping cycles. Then, a genetic algorithm was implemented to tune the stiffness and damping parameters for each of the configuration, minimizing the root mean square error between the model and experimental marker kinematics. The model was able to capture the deflection amplitude and harmonics of the CCMs with very good agreement and minimal to no phase shift.
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Звіти організацій з теми "SPARS"

1

Ahrens, David L., Daniel B. Olsen, and Azer P. Yalin. GRI-05-0138 Development of an Open Path Laser Ignition System for a Large Bore Natural. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 2005. http://dx.doi.org/10.55274/r0011965.

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Using a laser, as opposed to a conventional (electrical) spark plug, to create combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular, to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. These advantages may lead to an extension of the lean limit, an increase in engine thermal efficiency, and the concomitant benefits of reduced pollutant emissions. Presented in this paper is the design and implementation of a laser ignition system appropriate for a large bore natural gas engine. Design considerations include optimization of spark location, design of beam delivery system and optical plug, and mitigation of vibration and thermal effects. A single cylinder of a four-cylinder large bore natural gas engine is operated using laser ignition. Four different laser spark locations are examined. Comparisons are made between laser spark and conventional spark plug ignition.
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2

Ramirez, Ignacio, and Guillermo Sapiro. Universal Sparse Modeling. Fort Belvoir, VA: Defense Technical Information Center, March 2010. http://dx.doi.org/10.21236/ada520463.

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3

Lee, Sokbae (Simon), and Le-Yu Chen. Sparse Quantile Regression. The IFS, June 2020. http://dx.doi.org/10.1920/wp.cem.2020.3020.

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4

Bernard, Andrew, and Yuan Zi. Sparse Production Networks. Cambridge, MA: National Bureau of Economic Research, September 2022. http://dx.doi.org/10.3386/w30496.

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5

Adcock, Ben, Anyi Bao, John Davis Jakeman, and Akil Naryan. Compressed sensing with sparse corruptions: Fault-tolerant sparse collocation approximations. Office of Scientific and Technical Information (OSTI), April 2018. http://dx.doi.org/10.2172/1434573.

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6

Foltz, M. F., and L. R. Simpson. LLNL small-scale static spark machine: static spark sensitivity test. Office of Scientific and Technical Information (OSTI), August 1999. http://dx.doi.org/10.2172/14485.

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7

Lucas, Coraline, Sebastián Rodríguez, Fernando Sánchez, and José Buitrago. Exploring SPACs: Considerations for Latin American and Caribbean Entrepreneurs about Special Purpose Acquisition Companies. Inter-American Development Bank, June 2023. http://dx.doi.org/10.18235/0004939.

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Special Purpose Acquisition Companies (SPACs) can offer great advantages for companies planning on going public, including shortening times compared with conventional pathways to initial public offerings (IPOs). But SPACs can also present many risks, including subpar returns to investors and incomplete deals. Recently, SPACs have gained great media attention as markets saw a SPAC bubble boom and bust between 2020 and 2023, regulatory updates, and changing views about the value of SPACs.
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8

Sprechmann, Pablo, Ignacio Ramirez, Guillermo Sapiro, and Yonina Eldar. Collaborative Hierarchical Sparse Modeling. Fort Belvoir, VA: Defense Technical Information Center, March 2010. http://dx.doi.org/10.21236/ada519655.

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9

Deveci, Mehmet, Christian Robert Trott, and Sivasankaran Rajamanickam. Multi-threaded Sparse Matrix Sparse Matrix Multiplication for Many-Core and GPU Architectures. Office of Scientific and Technical Information (OSTI), January 2018. http://dx.doi.org/10.2172/1417260.

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10

Hill, Curtis W., Lynn A. Boatner, Dennis Tucker, James A. Kolopus, and Zhongyang Cheng. Spark Plasma Sintering of Ultracapacitors. Office of Scientific and Technical Information (OSTI), January 2016. http://dx.doi.org/10.2172/1236598.

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