Thematische Bibliographien / Spoof effects

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Auswahl der wissenschaftlichen Literatur zum Thema „Spoof effects“

Autor: Grafiati

Veröffentlicht am 28. Juni 2021

Zuletzt aktualisiert am 2. Februar 2022

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Zeitschriftenartikel zum Thema "Spoof effects"

Mercier, J. F., M. L. Cordero, S. Félix, A. Ourir und A. Maurel. „Classical homogenization to analyse the dispersion relations of spoof plasmons with geometrical and compositional effects“. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, Nr. 2182 (Oktober 2015): 20150472. http://dx.doi.org/10.1098/rspa.2015.0472.

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We show that the classical homogenization is able to describe the dispersion relation of spoof plasmons in structured thick interfaces with periodic unit cell being at the subwavelength scale. This is because the interface in the real problem is replaced by a slab of an homogeneous birefringent medium, with an effective mass density tensor and an effective bulk modulus. Thus, explicit dispersion relation can be derived, corresponding to guided waves in the homogenized problem. Contrary to previous effective medium theories or retrieval methods, the homogenization gives effective parameters depending only on the properties of the material and on the geometry of the microstructure. Although resonances in the unit cell cannot be accounted for within this low-frequency homogenization, it is able to account for resonances occurring because of the thickness of the interface and thus, to capture the behaviour of the spoof plasmons. Beyond the case of simple grooves in a hard material, we inspect the influence of tilting the grooves and the influence of the material properties.

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Mosavi, M. R., Z. Nasrpooya und M. Moazedi. „Advanced Anti-Spoofing Methods in Tracking Loop“. Journal of Navigation 69, Nr. 4 (04.03.2016): 883–904. http://dx.doi.org/10.1017/s0373463315001010.

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The Global Positioning System (GPS) has become widespread in many civilian applications. GPS signals are vulnerable to interference and even low-power interference can easily spoof GPS receivers. In this paper, two techniques are proposed based on correlators and adaptive filtering to diminish the effect of spoofing on GPS-based positioning. The suggested algorithms are implemented in the tracking loop of the receiver. As a first method, a high-resolution correlator is utilised to avoid big parts of the influence of interference. To improve the results, a multicorrelator technique is also employed. In the second method, an adaptive filter is used for estimating the parameters of authentic plus spoof signals. Interference elimination is performed by subtracting the estimated conflict effects from the measured correlation function. These techniques provide easy-to-implement quality assurance tools for anti-spoofing. As a primary step, in this article, the proposed algorithms have been implemented in a Software Receiver (SR) to prove the concept of idea in multipath-free environments.

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Qiu, Li Jun, und Su Ying Xu. „Exploration on the Dual Spool Design of Rotary Hydraulic Valve“. Advanced Materials Research 989-994 (Juli 2014): 2845–48. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.2845.

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There is also a monomer leak valve body on the single spool, Leakage between the guide groove affected the layout of the form guide groove. Two end faces of the single spool work in the different fluid pressure in the chamber. When the working pressure of the hydraulic system is high, the pressure differential will cause the spool bearings subject to large axial force. It will increase the resistance torque of bearing rotation. Effects of axial force also limits the increase spool diameter. Double spool valve with two spool rotation series manner. Each spool in the same pressure in the working medium. Eliminating the axial force of the valve body due to fluid pressure differential generated, also reduces the resistance to rotation of the spool moment and the impact of guide groove arrangement by oil leak, and also the commutation frequency of the rotary valve can be improved by increasing the diameter of the spool.

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Pan, Xu Dong, Guang Lin Wang und L. Zhang. „Simulation Study on Spool Edge’s Round Angle Effects on Spool Valve Orifice Discharge Characteristic“. Applied Mechanics and Materials 10-12 (Dezember 2007): 918–22. http://dx.doi.org/10.4028/www.scientific.net/amm.10-12.918.

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This paper deals with the effect on orifice discharge characteristic by the round angle of electro-hydraulic servo valve spool metering edge. The machining method of spool metering edge can cause micro round angle on the edge. This paper firstly provides 3D geometry model and computational grids of spool valve where the round angle’s range is 0-10μm and orifice opening is 0-40μm. Secondly calculates the flow rate of the orifice on the constant differential pressure circumstances. The numerical analysis is performed by using the commercial code ‘‘Fluent’’, and the numerical results show the complete flow field inside the valve. The analysis result is to obtain the influence of round angle on discharge characteristic, quantitatively. An experimental result is used in this paper to evaluate and validate the numerical analysis of the valve. The aim of this analysis is to provide a designation reference of the spool valves which are important parts of servo valve.

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Minias, Piotr, Radosław Włodarczyk, Adrian Surmacki und Tomasz Iciek. „Silver spoon effects on plumage quality in a passerine bird“. Royal Society Open Science 2, Nr. 6 (Juni 2015): 140459. http://dx.doi.org/10.1098/rsos.140459.

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A silver spoon effect means that individuals who develop under favourable circumstances enjoy a fitness or performance advantage later in life. While there is large empirical support for silver spoon effects acting on different life-history traits in birds, such as survival and reproduction, the evidence for the carry-over effects of rearing conditions on the quality of future plumage generations is lacking. Here, we examined whether abilities of individuals to undergo extensive post-juvenile moult may depend on the quality of juvenile plumage developed during the nestling phase in a small passerine showing large individual variation in the extent of post-juvenile moult, the greenfinch ( Carduelis chloris ). We found that high structural quality and carotenoid chroma of juvenile feathers were positively linked to the extent of post-juvenile moult in this species, thus allowing young birds to attain more adult-like plumage. Silver spoon effects mediated by the juvenile plumage quality were also found to have other fitness-related consequences, as individuals with high-quality juvenile feathers were in better condition during their first winter. As far as we are aware, the results provide the first correlative evidence for a silver spoon effect acting on general plumage quality in birds.

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Wang, He, Long Quan, Jiahai Huang, Guofang Gong und Xu Yang. „Reduction of steady flow torques in a single-stage rotary servo valve“. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, Nr. 4 (22.08.2018): 718–27. http://dx.doi.org/10.1177/0954408918793402.

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In this paper, geometry optimization of spool is proposed to reduce the steady flow torques in a single-stage rotary servo valve. The steady flow torques under different spool structures are studied by computational fluid dynamics simulation and experimental test and the most effective spool structure is found out. Then, the effects of geometry parameters on the steady flow torques are studied and an optimized solution for reduction of the steady flow torques is suggested by considering the optimization qualities and production costs. The results show that modification of the geometry of spool can make the jet angle at the orifices much closer to 90°, with almost no effect on the flow rate. Processing annular groove in the spool land with increased number of grooves on one side of the spool land is an effective way to reduce the steady flow torques. The maximum value of steady flow torques reduces with a gradual decrease in reduction as the external diameter of annular groove and the number of grooves increase. With the optimized spool structure, the maximum value of steady flow torques can be reduced significantly.

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Harrar, Vanessa, und Charles Spence. „A weighty matter: The effect of spoon size and weight on food perception“. Seeing and Perceiving 25 (2012): 199. http://dx.doi.org/10.1163/187847612x648288.

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When deciding on a product’s quality, we often pick it up to gauge its weight. If it’s heavy enough, we tend to think that it is good quality. We have recently shown that the weight of a dish can affect the taste and quality perception of the food it contains. Here, we varied the weight of spoons in order to determine whether the weight or size of the cutlery might influence taste perception. Teaspoons and tablespoons were tested, with one of each spoon-size artificially weighted with lead hidden into the handle (teaspoons: 2.35 and 5.67 g, and tablespoons: 3.73 and 10.84 g). Participants tasted yoghurt from each spoon and rated the yoghurt’s perceived density, price, sweetness, and pleasantness. Four within-participant ANOVAs were used to test the effects of spoon size and spoon weight on each attribute. The perceived density of the yoghurt was affected by the spoon’s weight, with yoghurt from light spoons being perceived as thicker than yoghurt sampled from a heavy spoon. The perceived price of the yoghurt also varied with spoon weight such that lighter spoons made the yoghurt taste more expensive. The most reliable effect was an interaction between spoon weight and spoon size on sweetness perception: heavy teaspoons and light tablespoons made the yoghurt appear sweeter. These data support the growing body of research demonstrating that tableware (and silverware) can affect the consumer’s judgements without their being aware.

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Pigeon, Gabriel, Marco Festa-Bianchet und Fanie Pelletier. „Long-term fitness consequences of early environment in a long-lived ungulate“. Proceedings of the Royal Society B: Biological Sciences 284, Nr. 1853 (19.04.2017): 20170222. http://dx.doi.org/10.1098/rspb.2017.0222.

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Cohort effects can be a major source of heterogeneity and play an important role in population dynamics. Silver-spoon effects, when environmental quality at birth improves future performance regardless of the adult environment, can induce strong lagged responses on population growth. Alternatively, the external predictive adaptive response (PAR) hypothesis predicts that organisms will adjust their developmental trajectory and physiology during early life in anticipation of expected adult conditions but has rarely been assessed in wild species. We used over 40 years of detailed individual monitoring of bighorn ewes ( Ovis canadensis ) to quantify long-term cohort effects on survival and reproduction. We then tested both the silver-spoon and the PAR hypotheses. Cohort effects involved a strong interaction between birth and current environments: reproduction and survival were lowest for ewes that were born and lived at high population densities. This interaction, however, does not support the PAR hypothesis because individuals with matching high-density birth and adult environments had reduced fitness. Instead, individuals born at high density had overall lower lifetime fitness suggesting a silver-spoon effect. Early-life conditions can induce long-term changes in fitness components, and their effects on cohort fitness vary according to adult environment.

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CHOWDHURY, SAYAM U., MOHAMMAD FOYSAL, M. ABDULLAH ABU DIYAN und SAKIB AHMED. „Discovery of an important wintering site of the Critically Endangered Spoon-billed Sandpiper Calidris pygmaea in the Meghna Estuary, Bangladesh“. Bird Conservation International 28, Nr. 2 (07.12.2017): 251–62. http://dx.doi.org/10.1017/s0959270917000247.

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SummaryThe Critically Endangered Spoon-billed Sandpiper Calidris pygmaeus is one of the most threatened migratory shorebirds in the world, breeding in Russia and wintering in Asia. The global population is declining rapidly and is projected to be extinct within a few decades without intervention. Here, we present the results of shorebird surveys in previously unrecognised site in Bangladesh along the Meghna Estuary, identified for the first time by using species distribution models. Counts and habitat preference of Spoon-billed Sandpipers and other endangered shorebirds are described here with notes on the global importance of the newly discovered site. The sum of the peak counts for each shorebird species across the two surveys was 25,993 including a minimum of 48 Spoon-billed Sandpipers. The majority of the Spoon-billed Sandpipers were observed during low tide while foraging (66.6%) and logistic regression testing for effects on the presence of foraging Spoon-billed Sandpiper indicate that they mainly preferred to forage on shallow mud. We summarise the threats to Spoon-billed Sandpipers and other birds in the new site that is currently not recognized as a Wetland of International Importance under the Ramsar Convention, although it fulfils several Ramsar Criteria. We also propose conservation and monitoring measures for long-term protection of the Spoon-billed Sandpiper and its habitat.

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Ruan, J., R. Burton, P. Ukrainetz und Y. M. Xu. „Two-dimensional pressure control valve“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 215, Nr. 9 (01.09.2001): 1031–38. http://dx.doi.org/10.1177/095440620121500903.

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The two-dimensional pressure control valve is a piloted control valve which functions by using both linear and rotary motions of a single spool. A groove on the spool land, incorporating a sensing channel, forms the pilot stage to control the pressure of a spool chamber, while the load pressure is fed to the other spool chamber. To sustain the balance of the force across the spool, the load pressure must follow the change of pressure variation along the groove while the spool is in rotary motion. The geometric parameters of the groove and the spool-to-sleeve clearance have significant effects on both the static and dynamic characteristics of the valve. Increasing the sectional size of the groove results in a large Reynolds number and the static property of the valve thus changes from that of linearity owing to the entrance effect. The linearity of the static property is also affected by the leakage through the spool-to-sleeve clearance. The dynamic characteristics of the valve are dependent upon both the structural parameters and the tune constant of the load. The stability and dynamic response were investigated under different structural parameters and time constants of the load using both linear theory and simulation methods. Experiments were designed to obtain the static and dynamic characteristics of the valve and the leakage through the pilot. A balance should be made between the linearity of the static property and the response speed; it was found that both fairly linear static and desired dynamic characteristics could be simultaneously maintained for the two-dimensional pressure control valve.

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Dissertationen zum Thema "Spoof effects"

Vrábľová, Žofia. „Pokročilé generování artefaktů falzifikátů do syntetických otisků prstů“. Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2021. http://www.nusl.cz/ntk/nusl-445551.

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The goal of this thesis is to extend the application for spoof effects generation into synthetic fingerprints with the possibility of generation of two new spoof effects together with annotations of generated damages. Spoof effects chosen for this thesis are areas with lower clarity and defects in spoof material. Those effects were analyzed, methods to generate those effects were designed and then implemented. According to testing, generation of two new added spoof effects led to reduction in quality of fingerprint images, as well as the value of the similarity score determined during identification. In comparison with the original solution, the quality of the fingerprints decreased more in the extended solution, the similarity score in the generation of separate spoof effect decreased overall approximately equally.

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Lee, Philina S. (Philina Sharlene) 1976. „Effects of the conserved proteins, Soj (ParA) and SpoOJ (ParB) on chromosome partitioning in Bacillus subtilis“. Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32255.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2004.
Includes bibliographical references.
The Par system contributes to stable inheritance of plasmids and chromosomes in diverse bacterial species. Faithful chromosome partitioning is important to dividing cells because anucleate, or chromosomeless, cells are not viable. Since the discovery of the Par system in low-copy number plasmids over 20 years ago, research has focused on characterizing its components: ParA, a DNA-binding ATPase, ParB, a DNA-binding protein that interacts with ParA, and parS, the site bound by ParB. How these proteins function to stabilize parS-containing plasmids or chromosomes remains to be elucidated. Less is known about the chromosomally-encoded Par systems. Intriguingly, in several organisms including Bacillus subtilis, chromosomally-encoded Par systems play important roles in cellular processes besides chromosome partitioning. This thesis focuses on characterizing the roles of Soj (ParA) and SpoOJ (ParB) of B. subtilis in chromosome partitioning. These proteins were first identified by their effects on sporulation. My results indicate that Soj and SpoOJ contribute to timely separation of replicated chromosomal origins, and argue against the model that SpoOJ anchors replicated origins to putative receptors in opposite halves of the cell. Additionally, I show that Soj and SpoOJ regulate replication of initiation, and propose that this regulation may occur by a similar genetic hierarchy through which they regulate initiation of sporulation.
by Philina S. Lee.
Ph.D.

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Almeida, Leah Zoe. „Legacies of early-life experiences on individual, cohort, and population performance of Lake Erie Walleye“. The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1614019841185563.

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Mitchell, Greg. „The importance of linking periods of the annual cycle for understanding life-history tradeoffs in a migratory songbird“. Thesis, 2011. http://hdl.handle.net/10214/3043.

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In migratory vertebrates, the optimal timing of successive life history stages is relatively inflexible. As a result, life history trade-offs that occur during breeding may influence individual success in subsequent stages because there is little time to mitigate negative costs that are incurred, or because the onset of subsequent stages is delayed. In migratory songbirds, understanding how breeding events carry over to influence individual success has been challenging because individuals are difficult to track once breeding is complete. I studied an island breeding population of migratory Savannah sparrows (Passerculus sandwichensis) and tracked individuals from breeding up until the onset of autumn migration. In Chapter 1, I investigated the effects of early life events on body condition during the pre-migratory period and first year apparent survival. I found that juveniles fledging from larger broods were in poorer condition at fledging, had lower fat stores prior to migration, and had lower first year apparent survival. In Chapter 2, I examined the effects of life history trade-offs made by adults during breeding on pre-migratory body condition and annual apparent survival. I did not find evidence for a trade-off between reproductive effort or date of breeding completion with annual apparent survival or body condition during the pre-migratory period, but instead found that adults with the highest reproductive effort and later dates of breeding completion were more likely to survive until the following year. In Chapter 3, I examined the effect of timing of breeding completion and fledging on the date of fall migration. I found that both variables had strong positive effects on date of departure. Together, my results suggest that successful migration in juveniles is influenced by early life events, but that any potential costs incurred by adults during the breeding season likely has little influence on survival during migration.

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Bücher zum Thema "Spoof effects"

Halliwell, Ian. Exoskeletal engine concept: Feasibility studies for medium and small thrust engines [final report]. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2001.

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Buchteile zum Thema "Spoof effects"

Kühl, Stefan. „Unwilling Recipients of Spoon-Feeding—The Unwanted Side Effects of University Reform“. In SpringerBriefs in Education, 39–49. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04087-5_4.

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Nitesh Mondal und Biswanath Datta. „Effect of Damping Length on Dynamic Performance of Two-Stage Two-Spool Electrohydraulic Servovalve“. In Fluid Mechanics and Fluid Power – Contemporary Research, 1213–22. New Delhi: Springer India, 2016. http://dx.doi.org/10.1007/978-81-322-2743-4_115.

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Tsai, Chia-Wen. „How Much Can Computers and Internet Help?“ In User Perception and Influencing Factors of Technology in Everyday Life, 248–64. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-1954-8.ch017.

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Computing education in Taiwan is ineffective. Most teaching efforts in private vocational schools have been devoted to helping students pass tests through a “spoon-feeding” teaching method. Under such constraints, students may lose their long-term competence in practical terms. In this study, the author conducted a series of quasi-experiments to examine the long-term effects of web-mediated problem-based learning (PBL), self-regulated learning (SRL), and their combinations on students’ computing skills over three years. The author re-examined students’ long-term computing skills three years after the start of the related course. Results reveal that effects of web-mediated PBL, SRL, and their combinations on students’ long-term computing skills are significant. The implications for scholars and teachers engaged in online learning were also discussed.

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Brück, Joanna. „Introduction: Identity and alterity in Bronze Age Britain and Ireland“. In Personifying Prehistory. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198768012.003.0004.

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In 2004, excavation in advance of the construction of a bypass around Mitchelstown in County Cork uncovered a number of pits on the banks of the Gradoge River (Kiely and Sutton 2007). On the bottom of one of these pits, three pottery vessels and a ceramic spoon had been laid on two flat stones. The pots had been deposited in a row: at the centre of the row was a small vessel that clearly models a human face with eyes, a protruding nose and ears, and, at the base of the pot, two feet (cover images). Oak charcoal from the pit returned a date of 1916–1696 cal BC. This find calls into question one of the basic conceptual building blocks that underpins our own contemporary understanding of the world—the distinction between people and objects—for it hints that some artefacts may have been imbued with human qualities and agentive capacities. This book is about the relationship between Bronze Age people and their material worlds. It explores the impact of the post-Enlightenment ‘othering’ of the non-human on our understanding of Bronze Age society. As we shall see, there is in fact considerable evidence to suggest that the categorical distinctions drawn in our own cultural context, for example between subject and object, self and other, and culture and nature, were not recognized or articulated in the same way during this period. So too contemporary forms of instrumental reason—encapsulated in a particular understanding of what constitutes logical, practical action and in the distinction we make between the ritual and the secular—have had a profound effect on how we view the Bronze Age world. Our understanding of the Bronze Age has undoubtedly changed dramatically since Christian Jürgensen Thomsen first popularized the term in his famous formulation of the three-age system in 1836 (Morris 1992). The very notion of a ‘Bronze Age’ foregrounds concepts of technical efficiency and advancement that doubtless chimed with the preoccupations and cultural values of Thomsen’s audience in the industrializing world in the nineteenth century.

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Konferenzberichte zum Thema "Spoof effects"

Manring, Noah D. „Modeling Spool-Valve Flow Forces“. In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59038.

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This paper has been written to reconsider the important topic of transient flow forces that act on spool-type hydraulic control valves. Though this subject has been addressed and somewhat laid to rest many years ago, the high-speed applications of our present day require a fresh look at this topic for gaining deeper insight into the significant contributions that determine the stability and frequency response of the hydraulic control valve. Over thirty years ago, it became an accepted practice to neglect the pressure transient flow-forces acting on the spool valve as they were deemed to be minor compared to the velocity effects of the spool itself. In this paper, flow force models with and without the pressure transient term are compared and it is shown that the historic practice of neglecting pressure transients may no longer be valid. As a result, this paper provides justification for considering the pressure transients in the analysis and may provide an explanation for some of the discrepancies that have existed between theoretical expectations and laboratory results.

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Khalil, Essam E., Eslam AbdelGhany, Mahmoud A. Fouad und Ahmed El-Sayed. „Effect of Pressure Recovery on Triple Spool Turbofan Engine Performance“. In 11th International Energy Conversion Engineering Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-3926.

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Meacock, A. J., und A. J. White. „The Effect of Water Injection on Multi-Spool Gas Turbine Behaviour“. In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53320.

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The injection of water droplets into industrial gas turbines is now common place and is central to several proposed advanced cycles. These cycles benefit from the subsequent reduction in compressor work, the increase in turbine work, and (in the case of recuperated cycles) reduction in compressor delivery temperature, which all act to increase the efficiency and power output. An investigation is presented here into the effect such water droplets will have on the operating point and flow characteristics of an aero-derivative gas turbine cycle. The paper first describes the development of a computer program to study the effects of water injection in multi-spool industrial gas turbines. The program can operate in two modes: the first uses pre-determined non-dimensional wet compressor maps to match the components and is instructive and fast but limited in scope; the second uses the compressor geometries as input and calculates the wet compressor operating conditions as and when required. As a result, it is more computationally demanding, but can cope with a wider range of circumstances. In both cases the compressor characteristics are calculated from a mean-line analysis using suitable loss, deviation and blockage models, coupled with Lagrangian-style droplet evaporation calculations. The program has been applied to a three-spool machine to address issues such as the effects of water-injection on power output and overall efficiency, and the off-design nature of the compressor operation.

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Speak, Trevor H., Robert J. Sellick, Vadim Kloos und Peter Jeschke. „Dual Drive Booster for a Two-Spool Turbofan: Performance Effects and Mechanical Feasibility“. In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42360.

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A novel two-spool turbofan engine configuration is described which uses a booster powered by both the LP and HP spool. Design and off-design performance analysis shows the operating characteristics of the configuration and a mechanical feasibility study of the gearbox is presented. The trends towards ever higher engine overall pressure ratio and bypass ratio have resulted in a combination of higher pressure ratio and lower blade speed in the booster compressor of conventional two spool turbofans. This combination gives rise to many stages in the booster and/or lower booster efficiency and also a higher degree of off-design miss-match between the core compressors. The current paper describes an engine architecture which aims to alleviate both these issues by powering the booster compressor from both LP and HP spools through an epicyclic gear system. We have called this engine architecture the Dual Drive Booster. The concept gives the engine designer greater flexibility to optimize component performance and work split, resulting in the potential for lower cruise SFC and higher hot day take-off thrust capability than current engine configurations. The gear system is described along with the mathematical derivation of the booster rotational speed in terms of LP and HP spool speeds. Both design point and off-design performance modelling has been conducted and comparison is made between a conventional turbofan and a turbofan fitted with the Dual Drive Booster. The results show a significant enhancement in take-off thrust due to the better speed match of the booster. The paper also describes the results of a preliminary study into the design and mechanical feasibility of the engine architecture and gear system. The presented concept is an alternative to the conventional turbofan and should be considered during the conceptual design of future aircraft engines.

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Merli, F., P. Z. Sterzinger, M. Dellacasagrande, L. Wiesinger, A. Peters, F. Heitmeir und E. Göttlich. „Unsteady Effects due to Rotor Purge Flow Variations in a Dual-Spool Turbine Setup“. In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15216.

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Abstract The paper discusses the impact of rotor purge flows on the unsteady flow field downstream of a two-stage, two-spool test turbine. The analyzed setup is representative of the second high-pressure turbine (HPT) and the first low-pressure turbine (LPT) stage in a modern turbofan aero-engine, with a turbine center frame (TCF) with non-turning struts in-between the two turbines. All measurements were carried out for an engine-representative test vehicle setup at the Transonic Test Turbine Facility at Graz University of Technology. The test rig features a secondary air system delivering five purge flows with independent temperature and mass flow control to the HPT and LPT cavities. This work extends the results shown in two recent publications analyzing the time-resolved flow through the same two-stage setup at fixed purge flow rates. The paper aims to provide additional input about the driving sources of unsteadiness in gas turbines for aeronautic applications, by isolating the HPT and LPT purge air contributions. The time-resolved flow field at the LPT exit was acquired with a Fast Response Aerodynamic Pressure Probe (FRAPP) for three different purge conditions (reference case, no HPT purge case, no LPT purge case), to separate and quantify the impact of HPT and LPT purge contributions on the main flow field. The so-called Rotor Synchronic Averaging (RSA) technique was used as phase-averaging approach, to account for the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was then applied to isolate the most important structures and identify their origins. The comparison of the three data-sets shows a significant influence of the HPT purge on the entire flow field at the LPT exit, even though the HPT is located far upstream, while the LPT purge impact appears to mostly affect the end-wall region.

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Yang, Roger. „Hydraulic Spool Valve Metering Notch Characterization Using CFD“. In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42420.

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This paper presents some results from an attempt to characterize hydraulic oil flow inside spool valves with different spool metering notches using Computational Fluid Dynamics (CFD). Hydraulic spool valve oil flow under different conditions has been simulated using a commercially available CFD software program. The fluid flow is assumed steady-state, incompressible, isothermal and normally in a turbulent mode. A complete simulation procedure is presented from parametric geometry creation with a 3-D solid CAD program through final post-processing of CFD results. Main focus of this study is to explore the effects of geometric parameters of notches on important hydraulic oil flow characteristics, such as flow force and discharge coefficients. Formulas, intended for predicting such flow forces and discharge coefficients at different stage of spool notch openings, have been generalized and summarized under certain conditions based on a CFD result database from groups of same types of notches. Results comparison to experimental data is also presented.

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Stammen, C. „Fluid Effects in Small Gaps: A Challenge for Sensor Application“. In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82335.

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This paper is motivated by the difficulty of pressure distribution measurement in the small gap between valve spool and housing or sleeve. The research project “Design of Balancing Grooves for Hydraulic Valves using Analysis of Flow and Pressure Distribution” at IFAS aims at providing a design tool for balancing grooves. It is based on the idea that the application of modern simulation techniques together with experimental results enhances knowledge about necessity and design of balancing grooves. Main influence on the pressure distribution is the gap height profile. Although valve spool and sleeve can be examined separately, it cannot be concluded to the geometrical information about the gap between these parts as accurate as needed to verify the simulation model. The paper describes the development of miniature pressure sensors made of manganin wire. Measurements showing the current results are presented. As an outlook, the integration of gap height measurement into the pressure sensors is proposed.

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McNea, Marshall, und Shanzhong (Shawn) Duan. „The Effects of Orifice Sizes on a Hydraulic Servo Valve Control System“. In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65239.

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Precision control for a force controlled hydraulic system can be achieved through the use of a flow controlled servo valve. Servo valves can be manufactured with a spool that is overlapped, an under lapped, or has a zero lap. A servo valve with a zero lap is desirable for a responsive hydraulic system without leakage, but has the disadvantage of creating a pressure pulse upon opening the valve. The hydraulic system for this setup involves having a double end, double action actuator that will have a cyclic motion generating multiple pressure waves in the system. Including an orifice in the system, which will function as a dampener, can reduce the pressure pulses. Traditional locations for orifices have been in the spool and on the actuator piston. For this hydraulic system design an external orifice will be introduced into the system via the use of an orifice plate included in the hydraulic fittings. This change allows for the ability to change the orifice size. Changing the orifice size to determine the effects on the systems control will be analyzed. The intended outcome is to demonstrate that different sized orifice plates will cause changes to the control system behavior so that an experimental formula will be established for this approach of a zero lap valve with an external damper for reduction of overshooting of dynamical behavior of the valve spool.

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Redmond, John A., Diann Brei, Jonathan Luntz, Alan L. Browne und Nancy L. Johnson. „Effect of bending on the performance of spool-packaged shape memory alloy actuators“. In SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, herausgegeben von Benjamin K. Henderson und M. Brett McMickell. SPIE, 2009. http://dx.doi.org/10.1117/12.816666.

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Gupta, K., R. Kumar, M. Tiwari und O. Prakash. „Effect of Rotary Inertia and Gyroscopic Moments on Dynamics of Two Spool Aeroengine Rotor“. In ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-045.

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The main objective of the paper is to study the effect of rotary inertia and gyroscopic moments due to lumped masses on the dynamics of two spool aeroengine rotors. Since the rotary inertia effect is well established, the thrust of the paper is on the effect of gyroscopic moments. Quantitative as well as qualitative aspects are studied. Effect of gyroscopics and rotary inertia on rotor critical speeds and unbalance response are studied for several rotors with particular reference to relative LP and HP rotor speeds. A two spool rig which resembles an actual aeroengine has been designed and built. Experiments have been conducted on two configurations of the rig in order to verify the theoretical results obtained by a formulation developed using the method of extended transfer matrices, for the two spool rotor with two intershaft bearings. A reasonably good correlation between the theoretical and experimental results is observed.

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