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Статті в журналах з теми "Mixing losses":
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Rose, M. G., and N. W. Harvey. "Turbomachinery Wakes: Differential Work and Mixing Losses." Journal of Turbomachinery 122, no. 1 (February 1, 1999): 68–77. http://dx.doi.org/10.1115/1.555429.
Анотація:
In this paper the mixing of stator wakes in turbomachinery is considered. An extension is made to the existing model of Denton (1993, ASME J. Turbomach., 115, pp. 621–656) which addresses the effects of acceleration before mixing. Denton showed that if a total pressure wake was accelerated, mixing loss diminished, and vice versa. Here a total temperature wake is shown to exhibit a reverse trend. An attempt is also made to understand better the work transfer process between a stator wake and a rotor. The paper concentrates on axial turbines, but a brief look at compressors is included. It is argued that the free-stream work is not the same as the wake work, and the concept of “Differential Work” is introduced. A simple steady velocity triangle based model is proposed to give an estimate of the ratio of wake work to free-stream work (μ, see later). The model is compared to an unsteady CFD result to offer some verification of the assumptions. It is concluded that the rotodynamic work process tends to reduce total pressure wake depths in turbines and compressors and therefore mixing losses. The mixing loss due to total temperature wakes is less strongly affected by the differential work process. [S0889-504X(00)00801-1]
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Zdobnov, M. I., N. A. Lavrov, and V. V. Shishov. "Analysis of losses in the mixing section of the central air conditioner using the entropy-statistical method." MATEC Web of Conferences 324 (2020): 03005. http://dx.doi.org/10.1051/matecconf/202032403005.
Анотація:
The article presents an entropy-statistical analysis of losses in the mixing section of a central air conditioner. The temperature and humidity of the outdoor and recirculating air were measured. The methodology for determining losses using the entropy-statistical method is presented in the work. The calculation of losses in the mixing section of the central air conditioner due to the mixing of air flows depending on the flow rate of the supply and recirculation air as well as due to hydraulic losses. A comparative analysis of the results is carried out and the distribution diagrams of the component losses are presented. Proposed conclusions regarding the way to reduce losses.
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Gao, J., Q. Zheng, G. Yue, and L. Sun. "Control of shroud leakage flows to reduce mixing losses in a shrouded axial turbine." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, no. 5 (October 3, 2011): 1263–77. http://dx.doi.org/10.1177/0954406211423324.
Анотація:
The losses caused by the leakage flows through the rotor tip clearance, and the mixing losses by the re-entering leakage into the main flow are considerable parts of the total losses in turbines. The main reason for the mixing losses is the different velocity components of main and leakage flows. This leads to shear stresses which cause increased turbulence and losses. This article presents a numerical investigation on three different configurations to control the leakage flows: (a) turning vanes are fixed onto the casing between the fins to turn the shroud leakage flow into the main flow direction in order to reduce the circumferential mixing losses; (b) honeycomb bands are inserted into the casing to weaken the leakage flow in the circumferential direction and reduce the circumferential mixing losses due to the special hexagon structure; and (c) downstream edge of the cavity is chamfered to reduce the radial velocity component of the leakage jet and the separation at the downstream edge, and also to reduce the streamwise mixing losses. A 1.5-stage axial turbine with high-aspect ratio blading was used in this study to investigate the sealing designs as mentioned. The flow simulation results of the three configurations were analysed and compared in this article.
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Kasumova, Rena J. "Four wave mixing and compensating losses in metamaterials." Superlattices and Microstructures 121 (September 2018): 86–91. http://dx.doi.org/10.1016/j.spmi.2018.07.013.
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Arbel, A., A. Shklyar, D. Hershgal, M. Barak, and M. Sokolov. "Ejector Irreversibility Characteristics." Journal of Fluids Engineering 125, no. 1 (January 1, 2003): 121–29. http://dx.doi.org/10.1115/1.1523067.
Анотація:
The present study analyzes and characterizes the irreversibility of the ejector’s internal processes in an effort to improve the understanding of the making of its overall performance. The analysis presented is based on entropy production methodology. Since entropy production is equivalent to performance losses, minimizing entropy production could serve as a tool for performance optimization. The three main internal processes forming sources of ejector irreversibility are mixing, kinetic energy losses, and normal shock wave. Comparison of these with those of an ideal mixing process, an ideal turbine-compressor system and stagnation conditions (of the flow after mixing) provides the benchmarks against which the actual overall performance is measured. By identifying the sources of irreversibility, the analysis provides a diagnostic tool for performance improvements. While irreversibility due to mixing can be eliminated by appropriate choice of gas and/or inlet conditions and an appropriate adjustable throat can eliminate losses associated with normal shock wave–kinetic energy losses can only be reduced but not totally eliminated.
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Schobeiri, M. T., and K. Pappu. "Optimization of Trailing Edge Ejection Mixing Losses: A Theoretical and Experimental Study." Journal of Fluids Engineering 121, no. 1 (March 1, 1999): 118–25. http://dx.doi.org/10.1115/1.2821991.
Анотація:
The aerodynamic effects of trailing edge ejection on mixing losses downstream of cooled gas turbine blades were experimentally investigated and compared with an already existing one-dimensional theory by Schobeiri (1989). The significant parameters determining the mixing losses and, therefore, the efficiency of cooled blades, are the ejection velocity ratio, the cooling mass flow ratio, the temperature ratio, the slot thickness ratio, and the ejection flow angle. To cover a broad range of representative turbine blade geometry and flow deflections, a General Electric power generation gas turbine blade with a high flow deflection and a NASA-turbine blade with intermediate flow deflection and different thickness distributions were experimentally investigated and compared with the existing theory. Comprehensive experimental investigations show that for the ejection velocity ratio μ = 1, the trailing edge ejection reduces the mixing losses downstream of the cooled gas turbine blade to a minimum, which is in agreement with the theory. For the given cooling mass flow ratios that are dictated by the heat transfer requirements, optimum slot thickness to trailing edge thickness ratios are found, which correspond to the minimum mixing loss coefficients. The results allow the turbine aerodynamicist to minimize the mixing losses and to increase the efficiency of cooled gas turbine blades.
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Moore, J., and R. Y. Adhye. "Secondary Flows and Losses Downstream of a Turbine Cascade." Journal of Engineering for Gas Turbines and Power 107, no. 4 (October 1, 1985): 961–68. http://dx.doi.org/10.1115/1.3239842.
Анотація:
The loss mechanisms and the behavior of secondary flows downstream of a large scale, linear turbine cascade have been investigated experimentally. A five-blade replica of the cascade used by Langston et al. at United Technologies Research Center was used for the present tests. Detailed flow measurements, using five-hole and three-hole probes, were made at four different planes, one just upstream of the trailing edge and the rest downstream. The secondary flow field at each measurement plane was found to be dominated by a single large passage vortex, which decayed in strength because of the mixing occurring in the flow. More than one-third of the losses were found to occur downstream of the trailing edge. This rise in total pressure loss in the present tests was almost entirely explained by a corresponding dissipation of the secondary kinetic energy of the flow. A mixing analysis of the flow was done to predict the additional losses due to “mixing” until the flow became completely uniform.
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Llobet, J. R., R. J. Gollan, and I. H. Jahn. "Effect of scramjet inlet vortices on fuel plume elongation and mixing rate." Aeronautical Journal 123, no. 1265 (June 21, 2019): 1032–52. http://dx.doi.org/10.1017/aer.2019.45.
Анотація:
ABSTRACTHypersonic air-breathing propulsion can improve cost and flexibility of Low Earth Orbit (LEO) satellite launch missions. However, at the high flight Mach numbers required for access-to-space, performance margins are extremely tight. Techniques to improve mixing efficiency can push this technology forward. However, these are required to produce a minimal increase in losses and heat loads to be viable. The use of inlet-generated vortices in scramjets for mixing enhancement was previously studied. These vortices interact with the injected fuel plume, stretching it and increasing its effective surface for mixing. Moreover, these vortices are intrinsic to the flowfield. Therefore, contrary to other methods, when using inlet vortices mixing is enhanced without producing additional heat loads or losses. This work studies the vortex-injection interaction through numerical RANS simulations. A non-dimensional variable defining the quality of the plume shape for mixing purposes is proposed. This parameter is used to assess the effect of vortex intensity and injector location on fuel plume shape. The results show the ability of inlet vortices to modify fuel plume shape significantly increasing fuel mixing rate with minimal impact on losses.
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Jackson, D. J., K. L. Lee, P. M. Ligrani, and P. D. Johnson. "Transonic Aerodynamic Losses Due to Turbine Airfoil, Suction Surface Film Cooling." Journal of Turbomachinery 122, no. 2 (February 1, 1999): 317–26. http://dx.doi.org/10.1115/1.555455.
Анотація:
The effects of suction surface film cooling on aerodynamic losses are investigated using an experimental apparatus designed especially for this purpose. A symmetric airfoil with the same transonic Mach number distribution on both sides is employed. Mach numbers range from 0.4 to 1.24 and match values on the suction surface of airfoils from operating aeroengines. Film cooling holes are located on one side of the airfoil near the passage throat where the free-stream Mach number is nominally 1.07. Round cylindrical and conical diffused film cooling hole configurations are investigated with density ratios from 0.8 to 1.3 over a range of blowing ratios, momentum flux ratios, and Mach number ratios. Also included are discharge coefficients, local and integrated total pressure losses, downstream kinetic energy distributions, Mach number profiles, and a correlation for integral aerodynamic losses as they depend upon film cooling parameters. The contributions of mixing and shock waves to total pressure losses are separated and quantified. These results show that losses due to shock waves vary with blowing ratio as shock wave strength changes. Aerodynamic loss magnitudes due to mixing vary significantly with film cooling hole geometry, blowing ratio, Mach number ratio, and (in some situations) density ratio. Integrated mixing losses from round cylindrical holes are three times higher than from conical diffused holes, when compared at the same blowing ratio. Such differences depend upon mixing losses just downstream of the airfoil, as well as turbulent diffusion of streamwise momentum normal to the airfoil symmetry plane. [S0889-504X(00)02202-9]
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Schobeiri, T. "Optimum Trailing Edge Ejection for Cooled Gas Turbine Blades." Journal of Turbomachinery 111, no. 4 (October 1, 1989): 510–14. http://dx.doi.org/10.1115/1.3262301.
Анотація:
The effect of trailing edge ejection on the flow downstream of a cooled gas turbine blade is investigated. Parameters that affect the mixing losses and therefore the efficiency of cooled blades are the ejection velocity ratio, the cooling mass flow ratio, the slot-width ratio, and the ejection angle. For ejection velocity ratio μ = 1, the trailing edge ejection reduces the mixing losses downstream to the cooled blade. For given cooling mass flow ratios, optimum slot-width/trailing edge ratios are found, which correspond to the minimum mixing loss coefficients.
Дисертації з теми "Mixing losses":
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Gilson, Laura (Laura Marie). "Mitigation of losses from hydrodynamic mixing in a hydrogen bromine Laminar flow battery." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103462.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 63-64).
The hydrogen bromine laminar flow battery is a promising technology for grid-scale energy storage. It dispenses with the expensive membrane used in traditional flow batteries, instead using laminar flow to maintain the separation of fluid streams. It also takes advantage of powerful, inexpensive chemical reactants. However, mixing between the fluid streams within the battery reduces its single-pass performance and cyclability. Conditions at the inlet junction where oxidant and electrolyte streams come together are thought to influence mixing. This work investigates the relationship between fluid flow at the inlet junction, mixing, and battery performance. Matching electrolyte- and oxidant-stream flow rates or velocities is predicted to cause less mixing than employing hydrodynamic focusing of the oxidant stream. When hydrodynamic focusing is used in channels with heights on the order 500 [mu]m or less, numerical simulations show recirculating flows at the inlet junction and experimental results show a decrease in limiting current. However, for matching inlet velocities or flow rates experimental results show limiting current consistent with predictions that assume no mixing. This result shows a path forward achieving higher power density in the hydrogen bromine laminar flow battery by prioritizing symmetry of the inlet flow conditions as the channel height is decreased.
by Laura M. Gilson.
S.M.
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Casey, Timothy. "The aerodynamic losses with the addition of film cooling in a high-speed annular cascade." Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1375.
Анотація:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Mechanical Engineering
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Firrito, Alessio. "Caractérisation de la turbulence et du mélange dans le canal inter-turbine." Thesis, Toulouse, ISAE, 2022. http://www.theses.fr/2022ESAE0004.
Анотація:
La réduction de consommation de carburant dans l'aéronautique est devenue un des principaux axes de recherche, afin de réduire l'empreinte environnementale de l'aviation, mais aussi pour réduire le coût d'exploitation des aéronefs. Les motoristes, outre l'étude des technologies de rupture, travaillent aussi à l'optimisation incrémentale des turbomachines afin d'en augmenter le rendement, en réduire le poids et en faciliter l'intégration.Les turbines sont à la fois les composants les plus lourds du moteur, et ceux dont leur rendement impacte le plus la consommation spécifique. Le lien entre la turbine haute pression et la turbine basse pression est assuré par le canal inter-turbine, étudié dans le cadre de cette thèse.Depuis une vingtaine d'années, les chercheurs et les industriels essaient d'optimiser ce composant, afin de le rendre plus compact et plus performant sur le plan aérodynamique. Ce processus d'optimisation est contraint par deux principales difficultés. Premièrement, la méconnaissance de l'écoulement en sortie de turbine haute pression, qui ne permet pas de quantifier exactement les non-homogénéités de l'écoulement en entrée. Deuxièmement, la forme globalement divergente des parois qui amplifient ces non-homogénéités d'entrée, en augmentant les pertes par mélange.Les études menées visent à quantifier les erreurs sur la prédiction des performances du canal inter-turbine par simulations numériques, induites par une mauvaise modélisation des pertes par mélange.Dans un premier temps, une configuration industrielle d'un banc d'essais est analysée, afin de démonter l'impact d'une mauvaise description des non-homogénéités de l'écoulement (appelés distorsions) sur les performances du canal inter-turbine. De nombreuses simulations numériques RANS stationnaires et instationnaires ont été effectuées pour répondre à cette question, et comparées sur la base des mesures. Les pertes par mélange calculées démontrent une forte dépendance des différents mécanismes à la distorsion elle-même, et à l'état de la turbulence en entrée. Ainsi, une compréhension plus complète du mécanisme d'interaction entre distorsion et turbulence s'avère nécessaire pour la bonne conception du composant. Or ce sont deux caractéristiques de l'écoulement qui sont mal connues en sortie de turbine haute pression, du fait de la difficulté à mesurer dans de tels environnements.Une fois les mécanismes de base identifiés, deux simplifications de la géométrie seront proposées, afin d'étudier séparément les effets de la divergence des parois externes (diffusion) et de la déviation de l'aubage, sur les pertes par mélange.Concernant la diffusion, l'évolution d'un sillage dans un divergent a été étudié sur un cas académique pour mieux comprendre et quantifier le mélange dans un tel environnement. Les simulations mettent en évidence le lien entre les pertes et la turbulence injectée en entrée. Une simulation de type LES permet de mieux comprendre ce phénomène d'interaction, et de vérifier la validité de l'approche RANS à deux équations pour laquelle un comportement anistrope de la turbulence est hors de portée.Concernant l'influence de la déviation, l'évolution des pertes par mélange, qui diminuent ou augmentent avec celle-ci, est un débat ouvert depuis les années '50 en environnement turbine. Jusqu'à maintenant, la communauté scientifique a essayé de répondre à cette question au travers d'analyses complexes et résolues en temps de turbines conventionnelles. L'originalité et la simplicité de l'approche proposée dans ce mémoire se base sur une comparaison de deux géométries de turbines co- et contra-rotatives, avec la capacité d'étudier le sillage dans son propre repère de génération, sans l'utilisation de post-traitements complexes.Enfin, les résultats et les connaissances acquises sur les configurations simplifiées seront appliquées à la géométrie industrielle, et donneront lieu à des recommandations de dimensionnement du canal inter-turbineReducing fuel consumption in aeronautics is one of the main areas of research, in order to reduce the environmental footprint of aviation, but also to reduce aircraft operational cost. In addition to studying disruptive technologies, engine manufacturers are also working on the incremental optimisation of turbomachinery to increase efficiency, reduce weight and facilitate integration.Turbines are both the heaviest engine components and those whose efficiency has the greatest impact on specific fuel consumption. The link between the high-pressure and the low-pressure turbine is provided by the inter-turbine duct, studied in this thesis.During the last twenty years, academics and companies have been trying to optimise this component, in order to make it shorter and more aerodynamically efficient. This optimisation process is constrained by two main difficulties. Firstly, the lack of knowledge of the high-pressure turbine outlet flow, which prevent accuracy on non-homogeneities (distortion) of the inlet flow quantification. Secondly, divergent shape of the walls amplifies these inlet distortions, increasing the mixing losses.The studies carried out aim at error quantification on the prediction of the inter-turbine duct performances by numerical simulations, induced by an improper modelling of mixing losses.In a first step, an industrial configuration of a test bench is analysed, in order to demonstrate the impact of an incorrect description of the flow distortions on the performances of the inter-turbine duct. Several steady and unsteady RANS numerical simulations have been performed to answer this question, and compared to experiments. The calculated mixing losses show a strong dependence of the different mechanisms on the distortion itself, and on the inlet turbulence. Thus, a more complete understanding of the interaction mechanism between distortion and turbulence is necessary for the proper design of the component. However, these are two flow characteristics that are poorly known at high-pressure turbine outlet, due to measuring difficulties in such environments.Once the main mechanism has been identified, two simplifications of the geometry will be proposed, in order to study separately the effects of the divergence of the external walls (diffusion) and of the deflection of the blade, on the mixing losses.Concerning diffusion, the evolution of a wake in a divergent has been studied on an academic case to better understand and quantify the mixing in such environments. The simulations highlight the link between losses and inlet turbulence. A LES simulation allows a better understanding of this interaction phenomenon, and to verify the validity of the two-equation models used in RANS approach, for which anisotropic turbulence behaviour is not modelled.Concerning the influence of the deviation, the evolution of the mixing losses, which decrease or increase with the deviation, has been an open debate since the 1950s in turbine environments. Until now, the scientific community has tried to answer this question through complex and time-resolved analyses of conventional turbines. The originality and simplicity of the approach proposed in this work is based on a comparison of two co- and contra-rotating turbine geometries, studing the wake in its own generation frame, without using complex post-processing.Finally, the results and knowledge gained from the simplified configurations will be applied to the industrial geometry, and will result in recommendations for the sizing of the inter-turbine channel
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NOBRE, CAMILA SEABRA. "MEASUREMENT OF POLARIZATION DEPENDENT LOSS USING FREQUENCY MIXING IN PHOTODIODES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=25739@1.
Анотація:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho apresenta um método teórico e experimental para medir Perda Dependente de Polarização (PDL) em sistemas ópticos. Este método basea-se na forma como duas componentes de polarização ortogonais da luz moduladas em amplitude por duas frequências distintas são acopladas no detector após a transmissão pelo dispositivo sob caracterização. No presente trabalho é realizado um estudo acerca das propriedades da luz e das técnicas tradicionais utlizadas para medir PDL. Antes da caracterização das medidas de PDL, foi realizado o alinhamento do dispositivo de teste (DUT), ou seja, do sistema que vai emular a PDL, a fim de garantir que o mesmo estivesse com as perdas ópticas minimizadas. Em seguida, conectou-se o DUT à configuração montada no laboratório, sendo realizado os ajustes de polarização e supressão das portadoras ópticas. Neste método é possível calcular o valor da PDL e da na orientação na Esfera de Poincaré.
This work presents a theoretic and experimental method for Polarization Dependent Loss (PDL) measurement in optical systems. This method is based on how two orthogonal polarization components both modulated in amplitude by two different frequency are coupled in the detector. In this present work a study is performed about light properties and traditional techniques used to peform PDL measurement. Before the characterization of PDL measures the alignment of the device under test (DUT) was performed to make sure that optical losses were minimized in the system which will emulate the PDL. Then, the DUT was connected to the experimental setup to optical carriers suppression and polarization alignment. In this method is possible to calculate the PDL value and its orientation on the Poincaré sphere.
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Pavlíček, David. "CFD modelování mísení kapalin v potrubí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-387733.
Анотація:
This work is focused on computational modelling of mixing fluids in pipeline with static mixers. Main objective is to analyze several selected static mixers in a particular industrial application, namely dosing of the aluminium sulphate solution in the clarification process for potable water treatment. The analysis focuses on the degree of mixedness and pressure loss of individual mixers. Further, the aim of this work is to process the search of available types of static mixers. The benefit of this work is at least an effort to motivate the reader to deeper understanding of the mixing fluids, especially by static mixers.
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Mennesson, Stéphane. "Les droits sur choses de genre." Thesis, La Réunion, 2017. http://www.theses.fr/2017LARE0041/document.
Анотація:
Cette étude a pour objet de démontrer la possibilité d'existence de droits sur des choses de genre, c'est-à-dire sur des choses définies de manière générale et d'exposer ensuite ses implications. Cette hypothèse est traditionnellement écartée par la théorie des biens, qui n'admet l'existence de droits de propriété et de droits réels que sur des choses individuellement déterminées. Le principe d'une réservation de choses génériquement déterminées est pourtant concevable et mérite, dans ces conditions, être reconnu. Les conséquences principales de cette reconnaissance sont au nombre de deux. Les droits sur choses de genre présentent tout d'abord la particularité de pouvoir survivre à la confusion de la chose qui constitue leur assiette. Ils présentent également la particularité plus remarquable de pouvoir, dans un assez grand nombre d'hypothèses, survivre à la disparition matérielle ou juridique de la chose qui en constitue l'objetThe purpose of this study is to demonstrate the possibility of existence of rights over generic things, i.e things whose constitution is determined in consideration of generic features, and to present its implications. Property law has, historically, never admitted the fact that a right could be established on things other than those which are individually determined, and can be refered to as "this" thing. Rights over generic things are, nevertheless, a reality and therefore deserved to be recognized. They have two main characteristics. First of all, they have the ability to survive the mixing of their object with other identical things. They can also, in a rather important number of cases, survive the material or juridical loss of their object
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Fiore, Maxime. "Influence of cavity flow on turbine aerodynamics." Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0013/document.
Анотація:
Afin de faire face aux fortes températures rencontrées par les composantsen aval de la chambre de combustion, des prélèvements d’air plus frais sont réalisésau niveau du compresseur. Cet air alimente les cavités en pied de turbine et refroidiles disques rotor permettant d’assurer le bon fonctionnement de la turbine.Ce manuscrit présente une étude numérique de l’effet de ces écoulements de cavitéau pied de la turbine sur ses performances aérodynamiques. Les phénomènesd’interaction entre l’air de cavité en pied de turbine et l’air de veine principal est unphénomène encore difficilement compris. L’étude de ces phénomènes est réalisée autravers de différentes approches numériques (RANS, LES et LES-LBM) appliquéesà deux configurations pour lesquelles des résultats expérimentaux s ont disponibles.Une première configuration en grille d’aube linéaire en amont de laquelle différentesgéométries d’entrefer (interface entre plateforme rotor et stator) et débits de cavitépouvaient être variés. Une seconde configuration annulaire composée de deux étagesde turbine comprenant les cavités en pied et plus proche d’une configuration industrielle.Les pertes additionnelles associées à l’écoulement de cavité sont mesurées etétudiées à l’aide d’une méthode basée sur l’exergie (bilans d’énergie dans l’objectifde générer du travail)In order to deal with high temperatures faced by the components downstreamof the combustion chamber, some relatively cold air is bled at the compressor.This air feeds the cavities under the turbine main annulus and cool down the rotordisks ensuring a proper and safe operation of the turbine. This thesis manuscriptintroduces a numerical study of the effect of the cavity flow close to the turbine hubon its aerodynamic performance. The interaction phenomena between the cav-ity andmain annulus flow are not currently fully understood. The study of these phenomenais performed based on different numerical approaches (RANS, LES and LES-LBM)applied to two configurations for which experimental results are avail-able. A linearcascade configuration with an upstream cavity and various rim seal geometries(interface between rotor and stator platform) and cavity flow rate avail-able. Arotating configuration that is a two stage turbine including cavities close to realisticindustrial configurations. Additional losses incurred by the cavity flow are measuredand studied using a method based on exergy (energy balance in the purpose togenerate work)
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Kosmata, Marcel. "Elastische Rückstoßatomspektrometrie leichter Elemente mit Subnanometer-Tiefenauflösung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-84041.
Анотація:
In der vorliegenden Arbeit wird erstmals das QQDS-Magnetspektrometer für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Helmholtz-Zentrum Dresden-Rossendorf umfassend vorgestellt. Zusätzlich werden sowohl alle auf die Analytik Einfluss nehmenden Parameter untersucht als auch Methoden und Modelle vorgestellt, wie deren Einfluss vermieden oder rechnerisch kompensiert werden kann. Die Schwerpunkte dieser Arbeit gliedern sich in fünf Bereiche. Der Erste ist der Aufbau und die Inbetriebnahme des QQDS-Magnetspektrometers, der zugehörige Streukammer mit allen Peripheriegeräten und des eigens für die höchstauflösende elastische Rückstoßanalyse entwickelten Detektors. Sowohl das umgebaute Spektrometer als auch der im Rahmen dieser Arbeit gebaute Detektor wurden speziell an experimentelle Bedingungen für die höchstauflösende Ionenstrahlanalytik leichter Elemente angepasst und erstmalig auf einen routinemäßigen Einsatz hin getestet. Der Detektor besteht aus zwei Komponenten. Zum einen befindet sich am hinteren Ende des Detektors eine Bragg-Ionisationskammer, die zur Teilchenidentifikation genutzt wird. Zum anderen dient ein Proportionalzähler, der eine Hochwiderstandsanode besitzt und direkt hinter dem Eintrittsfenster montiert ist, zur Teilchenpositionsbestimmung im Detektor. Die folgenden zwei Schwerpunkte beinhalten grundlegende Untersuchungen zur Ionen-Festkörper-Wechselwirkung. Durch die Verwendung eines Magnetspektrometers ist die Messung der Ladungszustandsverteilung der herausgestreuten Teilchen direkt nach einem binären Stoß sowohl möglich als auch für die Analyse notwendig. Aus diesem Grund werden zum einen die Ladungszustände gemessen und zum anderen mit existierenden Modellen verglichen. Außerdem wird ein eigens entwickeltes Modell vorgestellt und erstmals im Rahmen dieser Arbeit angewendet, welches den ladungszustandsabhängigen Energieverlust bei der Tiefenprofilierung berücksichtigt. Es wird gezeigt, dass ohne die Anwendung dieses Modells die Tiefenprofile nicht mit den quantitativen Messungen mittels konventioneller Ionenstrahlanalytikmethoden und mit der Dickenmessung mittels Transmissionselektronenmikroskopie übereinstimmen, und damit falsche Werte liefern würden. Der zweite für die Thematik wesentliche Aspekt der Ionen-Festkörper-Wechselwirkung, sind die Probenschäden und -modifikationen, die während einer Schwerionen-bestrahlung auftreten. Dabei wird gezeigt, dass bei den hier verwendeten Energien sowohl elektronisches Sputtern als auch elektronisch verursachtes Grenzflächendurchmischen eintreten. Das elektronische Sputtern kann durch geeignete Strahlparameter für die meisten Proben ausreichend minimiert werden. Dagegen ist der Einfluss der Grenzflächendurchmischung meist signifikant, so dass dieser analysiert und in der Auswertung berücksichtigt werden muss. Schlussfolgernd aus diesen Untersuchungen ergibt sich für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Rossendorfer 5-MV Tandembeschleuniger, dass die geeignetsten Primärionen Chlor mit einer Energie von 20 MeV sind. In Einzelfällen, wie zum Beispiel der Analyse von Bor, muss die Energie jedoch auf 6,5 MeV reduziert werden, um das elektronische Sputtern bei der notwendigen Fluenz unterhalb der Nachweisgrenze zu halten. Der vierte Schwerpunkt ist die Untersuchung von sowohl qualitativen als auch quantitativen Einflüssen bestimmter Probeneigenschaften, wie beispielsweise Oberflächenrauheit, auf die Form des gemessenen Energiespektrums beziehungsweise auf das analysierte Tiefenprofil. Die Kenntnis der Rauheit einer Probe an der Oberfläche und an den Grenzflächen ist für die Analytik unabdingbar. Als Resultat der genannten Betrachtungen werden die Einflüsse von Probeneigenschaften und Ionen-Festkörper-Wechselwirkungen auf die Energie- beziehungsweise Tiefenauflösung des Gesamtsystems beschrieben, berechnet und mit der konventionellen Ionenstrahlanalytik verglichen. Die Möglichkeiten der höchstauflösenden Ionenstrahlanalytik werden zudem mit den von anderen Gruppen veröffentlichten Komplementärmethoden gegenübergestellt. Der fünfte und letzte Schwerpunkt ist die Analytik leichter Elemente in ultradünnen Schichten unter Berücksichtigung aller in dieser Arbeit vorgestellten Modelle, wie die Reduzierung des Einflusses von Strahlschäden oder die Quantifizierung der Elemente im dynamischen Ladungszustandsnichtgleichgewicht. Es wird die Tiefenprofilierung von Mehrschichtsystemen, bestehend aus SiO2-Si3N4Ox-SiO2 auf Silizium, von Ultra-Shallow-Junction Bor-Implantationsprofilen und von ultradünnen Oxidschichten, wie zum Beispiel High-k-Materialien, demonstriertIn this thesis the QQDS magnetic spectrometer that is used for high resolution ion beam analysis (IBA) of light elements at the Helmholtz-Zentrum Dresden-Rossendorf is presented for the first time. In addition all parameters are investigated that influence the analysis. Methods and models are presented with which the effects can be minimised or calculated. There are five focal points of this thesis. The first point is the construction and commissioning of the QQDS magnetic spectrometer, the corresponding scattering chamber with all the peripherals and the detector, which is specially developed for high resolution elastic recoil detection. Both the reconstructed spectrometer and the detector were adapted to the specific experimental conditions needed for high-resolution Ion beam analysis of light elements and tested for routine practice. The detector consists of two compo-nents. At the back end of the detector a Bragg ionization chamber is mounted, which is used for the particle identification. At the front end, directly behind the entrance window a proportional counter is mounted. This proportional counter includes a high-resistance anode. Thus, the position of the particles is determined in the detector. The following two points concern fundamental studies of ion-solid interaction. By using a magnetic spectrometer the charge state distribution of the particles scattered from the sample after a binary collision is both possible and necessary for the analysis. For this reason the charge states are measured and compared with existing models. In addition, a model is developed that takes into account the charge state dependent energy loss. It is shown that without the application of this model the depth profiles do not correspond with the quantitative measurements by conventional IBA methods and with the thickness obtained by transmission electron microscopy. The second fundamental ion-solid interaction is the damage and the modification of the sample that occurs during heavy ion irradiation. It is shown that the used energies occur both electronic sputtering and electronically induced interface mixing. Electronic sputtering is minimised by using optimised beam parameters. For most samples the effect is below the detection limit for a fluence sufficient for the analysis. However, the influence of interface mixing is so strong that it has to be included in the analysis of the layers of the depth profiles. It is concluded from these studies that at the Rossendorf 5 MV tandem accelerator chlorine ions with an energy of 20 MeV deliver the best results. In some cases, such as the analysis of boron, the energy must be reduced to 6.5 MeV in order to retain the electronic sputtering below the detection limit. The fourth focus is the study of the influence of specific sample properties, such as surface roughness, on the shape of a measured energy spectra and respectively on the analysed depth profile. It is shown that knowledge of the roughness of a sample at the surface and at the interfaces for the analysis is needed. In addition, the contribution parameters limiting the depth resolution are calculated and compared with the conventional ion beam analysis. Finally, a comparison is made between the high-resolution ion beam analysis and complementary methods published by other research groups. The fifth and last focus is the analysis of light elements in ultra thin layers. All models presented in this thesis to reduce the influence of beam damage are taken into account. The dynamic non-equilibrium charge state is also included for the quantification of elements. Depth profiling of multilayer systems is demonstrated for systems consisting of SiO2-Si3N4Ox-SiO2 on silicon, boron implantation profiles for ultra shallow junctions and ultra thin oxide layers, such as used as high-k materials
9
Fernandes, Gil Gonçalo Martins. "Optical and digital signal processing in space-division multiplexing transmission systems." Doctoral thesis, 2018. http://hdl.handle.net/10773/28329.
Анотація:
The present thesis focuses on the development of optical and digital signal processing techniques for coherent optical transmission systems with spacedivision multiplexing (SDM). According to the levels of spatial crosstalk, these systems can be grouped in the ones with and the ones without spatial selectivity; drastically changing its operation principle. In systems with spatial selectivity, the mode coupling is negligible and therefore, an arbitrary spacial channel can be independently routed through the optical network and post-processed at the optical coherent receiver. In systems without spatial selectivity, mode coupling plays a key role in a way that spatial channels are jointly transmitted and post-processed at the optical coherent receiver.
With this in mind, optical switching techniques for SDM transmission systems with spatial selectivity are developed, whereas digital techniques for space-demultiplexing are developed for SDM systems without spatial selectivity. With the purpose of developing switching techniques, the acoustic-optic effect is analyzed in few-mode fibers (FMF)s and in multicore fibers (MCF)s. In FMF, the signal switching between two arbitrary modes using flexural or longitudinal acoustic waves is numerically and experimentally demonstrated.
While, in MCF, it is shown that a double resonant coupling, induced by flexural acoustic waves, allows for the signal switching between two arbitrary cores. Still in the context of signal switching, the signal propagation in the multimodal nonlinear regime is analyzed. The nonlinear Schrödinger equation is deduced in the presence of mode coupling, allowing the meticulous
analysis of the multimodal process of four-wave mixing. Under the right conditions, it is shown that such process allows for the signal switching between distinguishable optical modes.
The signal representation in higher-order Poincaré spheres is introduced and analyzed in order to develop digital signal processing techniques. In this representation, an arbitrary pair of tributary signals is represented in a Poincaré sphere, where the samples appear symmetrically distributed around a symmetry plane. Based on this property, spatial-demultiplexing and mode
dependent loss compensation techniques are developed, which are independent of the modulation format, are free of training sequences and tend to be robust to frequency offsets and phase fluctuations. The aforementioned techniques are numerically validated, and its performance is assessed through the calculation of the remaining penalty in the signal-to-noise ratio of the post-processed signal. Finally, the complexity of such techniques is analytically described in terms of real multiplications per sample.A presente tese tem por objectivo o desenvolvimento de técnicas de processamento ótico e digital de sinal para sistemas coerentes de transmissão ótica com multiplexagem por diversidade espacial. De acordo com a magnitude de diafonia espacial, estes sistemas podem ser agrupados em sistemas com e sem seletividade espacial, alterando drasticamente o seu princípio de funcionamento. Em sistemas com seletividade espacial, o acoplamento modal é negligenciável e, portanto, um canal espacial arbitrário pode ser encaminhado de forma independente através da rede ótica e pós-processado no recetor ótico coerente. Em sistemas sem seletividade espacial, o acoplamento modal tem um papel fulcral pelo que os canais espaciais são transmitidos e pós-processados conjuntamente. Perante este cenário, foram desenvolvidas técnicas de comutação entre canais espaciais para sistemas com seletividade espacial, ao passo que para sistemas sem seletividade espacial, foram desenvolvidas técnicas digitais de desmultiplexagem espacial. O efeito acústico-ótico foi analisado em fibras com alguns modos (FMF) e em fibras com múltiplos núcleos (MCF) com o intuito de desenvolver técnicas de comutação de sinal no domínio ótico. Em FMF, demonstrou-se numérica e experimentalmente a comutação do sinal entre dois modos de propagação arbitrários através de ondas acústicas transversais ou longitudinais, enquanto, em MCF, a comutação entre dois núcleos arbitrários é mediada por um processo de acoplamento duplamente ressonante induzido por ondas acústicas transversais. Ainda neste contexto, analisou-se a propagação do sinal no regime multimodal não linear. Foi deduzida a equação não linear de Schrödinger na presença de acoplamento modal, posteriormente usada na análise do processo multimodal de mistura de quatro ondas. Nas condições adequadas, é demonstrado que este processo permite a comutação ótica de sinal entre dois modos de propagação distintos. A representação de sinal em esferas de Poincaré de ordem superior é introduzida e analisada com o objetivo de desenvolver técnicas de processamento digital de sinal. Nesta representação, um par arbitrário de sinais tributários é representado numa esfera de Poincaré onde as amostras surgem simetricamente distribuídas em torno de um plano de simetria. Com base nesta propriedade, foram desenvolvidas técnicas de desmultiplexagem espacial e de compensação das perdas dependentes do modo de propagação, as quais são independentes do formato de modulação, não necessitam de sequências de treino e tendem a ser robustas aos desvios de frequência e às flutuações de fase. As técnicas referidas foram validadas numericamente, e o seu desempenho é avaliado mediante a penalidade remanescente na relação sinal-ruído do sinal pós-processado. Por fim, a complexidade destas é analiticamente descrita em termos de multiplicações reais por amostra.
Programa Doutoral em Engenharia Eletrotécnica
10
Zhen, Yurong. "Plasmonic properties and applications of metallic nanostructures." Thesis, 2013. http://hdl.handle.net/1911/72071.
Анотація:
Plasmonic properties and the related novel applications are studied on various
types of metallic nano-structures in one, two, or three dimensions. For 1D nanostructure,
the motion of free electrons in a metal-film with nanoscale thickness is confined in
its normal dimension and free in the other two. Describing the free-electron motion at
metal-dielectric surfaces, surface plasmon polariton (SPP) is an elementary excitation
of such motions and is well known. When further perforated with periodic array of
holes, periodicity will introduce degeneracy, incur energy-level splitting, and facilitate
the coupling between free-space photon and SPP. We applied this concept to achieve
a plasmonic perfect absorber. The experimentally observed reflection dip splitting
is qualitatively explained by a perturbation theory based on the above concept. If
confined in 2D, the nanostructures become nanowires that intrigue a broad range of
research interests. We performed various studies on the resonance and propagation
of metal nanowires with different materials, cross-sectional shapes and form factors,
in passive or active medium, in support of corresponding experimental works. Finite-
Difference Time-Domain (FDTD) simulations show that simulated results agrees well
with experiments and makes fundamental mode analysis possible. Confined in 3D,
the electron motions in a single metal nanoparticle (NP) leads to localized surface
plasmon resonance (LSPR) that enables another novel and important application:
plasmon-heating. By exciting the LSPR of a gold particle embedded in liquid, the
excited plasmon will decay into heat in the particle and will heat up the surrounding
liquid eventually. With sufficient exciting optical intensity, the heat transfer from NP
to liquid will undergo an explosive process and make a vapor envelop: nanobubble.
We characterized the size, pressure and temperature of the nanobubble by a simple
model relying on Mie calculations and continuous medium assumption. A novel
effective medium method is also developed to replace the role of Mie calculations.
The characterized temperature is in excellent agreement with that by Raman scattering.
If fabricated in an ordered cluster, NPs exhibit double-resonance features and
the double Fano-resonant structure is demonstrated to most enhance the four-wave
mixing efficiency.
Книги з теми "Mixing losses":
1
Riggins, David W. Analysis of losses in supersonic mixing and reacting flows. Washington, D. C: American Institute of Aeronautics and Astronautics, 1991.
2
Center, Goddard Space Flight, ed. Abundance anomalies of carbon and nitrogen in the IUE spectra of Algol-type interacting binaries: Final status report, NASA grant NAG 5-1107, 1 December 1988 - 30 November 1990. [Greenbelt, Md.]: NASA Goddard Space Flight Center, 1990.
3
Mufwene, Salikoko, and Anna Maria Escobar, eds. The Cambridge Handbook of Language Contact. Cambridge University Press, 2022. http://dx.doi.org/10.1017/9781009105965.
Анотація:
Language contact - the linguistic and social outcomes of two or more languages coming into contact with each other - starts with the emergence of multilingual populations. Multilingualism involving plurilingualism can have various consequences beyond borrowing, interference, and code-mixing and -switching, including the emergence of lingua francas and new language varieties, as well as language endangerment and loss. Bringing together contributions from an international team of scholars, this Handbook - the second in a two-volume set - engages the reader with the manifold aspects of multilingualism and provides state-of-the-art research on the impact of population structure on language contact. It begins with an introduction that presents the history of the scholarship on the subject matter. The chapters then cover various processes and theoretical issues associated with multilingualism embedded in specific population structures worldwide as well as their outcomes. It is essential reading for anybody interested in how people behave linguistically in multilingual or multilectal settings.
Частини книг з теми "Mixing losses":
1
Steward, Dwight. "Case Study 2: Truck Driver v. Concrete Mixing Company." In Economic Losses and Mitigation after an Employment Termination, 101–5. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-88364-5_10.
2
Chambart, P., and Ph Schnoebelen. "Mixing Lossy and Perfect Fifo Channels." In CONCUR 2008 - Concurrency Theory, 340–55. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-85361-9_28.
3
Maasoumi, Esfandiar. "Mixing Forecasts in Linear Simultaneous Equations Under Quadratic Loss." In Contributions to Consumer Demand and Econometrics, 176–88. London: Palgrave Macmillan UK, 1992. http://dx.doi.org/10.1007/978-1-349-12221-9_10.
4
Hollowell, David, and Icko Iben. "Nucleosynthesis and mixing in low- and intermediate-mass AGB stars." In Atmospheric Diagnostics of Stellar Evolution: Chemical Peculiarity, Mass Loss, and Explosion, 38–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/bfb0034548.
5
Deddy Hermawan, Yulius, Dedy Kristanto, and Hariyadi. "Oil Losses Problem in Oil and Gas Industries." In Crude Oil - New Technologies and Recent Approaches [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97553.
Анотація:
Oil losses is a problem that often arises in oil and gas industries either in onshore or offshore area. There is a loss discrepancy between total quantities from shippers and measurement in the storage tanks; the total sending volume is lower than the measured volume in the mixing tank in a gathering station; this is known as oil losses. When this occurs, an agreement to determine a fair share of the losses must be made. There are two categories of oil losses, they are individual and group losses. Individual loss occurs when oil from one shipper has not been mixed yet with other oils. This includes emulsion and evaporative losses. Group loss occurs during mixing oils in the same storage tank or pipeline. Furthermore, by knowing the causes of oil losses, a way to minimize oil losses can be determined.
6
Cohen, Andrew S. "The Physical Environment of Lakes." In Paleolimnology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195133530.003.0007.
Анотація:
Before discussing paleolimnological archives, we need to consider those aspects of limnology that regulate how information is produced, transmitted, and filtered through the water column. Although many limnological processes leave behind sedimentary clues of their existence or intensity and are thus amenable to paleolimnological analysis, others leave little or no detectable trace. Our consideration of limnology here emphasizes the former. Throughout the next three chapters we will examine the properties of lakes, the implications of these properties for paleolimnology, and the types of physical, chemical, and biological information that can be transcribed into sedimentary archives. Physical processes in lakes are of interest because they act as intermediary hydroclimate filters between external forcing events of interest, like climate, and the paleolimnological record. For example, understanding the hydrology of a lake is important because water inputs and outputs, which are often controlled by climate, determine lake levels, which in turn are recorded by ancient shoreline elevations, or indirectly by salinity indicators. Light and heat penetration regulate the distribution of organisms and the mixing of the water column, recorded by the distribution of various fossils, sediment types, and geochemical characteristics of sediments. Also, current and wave activity affect the transport of sedimentary particles and therefore the distribution of sediment types around a lake basin. Understanding these physical processes therefore provides us with a means of linking sedimentological, geochemical, and paleobiological records of lake deposits to the external environment. Water enters and exits lakes through a variety of paths that comprise part of the earth’s hydrological cycle. The lake components of this cycle include a series of inputs and outputs of water, which in combination with the morphometry of the lake basin, collectively determine the lake’s level. Inputs include precipitation, surface runoff from rivers, and groundwater discharge into the lake. Outflows include surface outflow, evaporation, evapotranspiration losses from emergent aquatic plants, groundwater recharge, and hydration reactions with underlying sediments. If water inputs and outputs for a lake are equal over a short time span, the lake surface elevation will remain constant. This is approximately the case in most lakes that are surficially open basins.
7
"Challenges for Diadromous Fishes in a Dynamic Global Environment." In Challenges for Diadromous Fishes in a Dynamic Global Environment, edited by Heidi K. Swanson and Karen A. Kidd. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch29.
Анотація:
<em>Abstract</em>.-While there has been much recent research conducted on the effects of semelparous anadromous (sea-run) fishes on nutrient cycling and productivity in freshwater lakes, we know very little about how iteroparous anadromous fishes may affect these processes and ecosystems. Although iteroparous sea-run fishes do not contribute mass postspawning carcass additions to freshwater systems, nutrients may still be transported from marine to freshwater environments through deposition of eggs, metabolic losses, and postspawning/overwintering mortality. As well, some iteroparous sea-run species spend significant time growing to juvenile and smolt stages in freshwater where they may affect top-down or bottom-up changes in food web structure. The goals of this study were to (1) conduct a preliminary investigation into the effect of sea-run Arctic char <em>Salvelinus alpinus </em>on food web structure in coastal lakes in the central Canadian Arctic, and (2) semiquantitatively assess the direction of net nutrient transport achieved by anadromous Arctic char during annual migrations to the sea. In 2006, fishes and macroinvertebrates were collected from four lakes near Hope Bay, Nunavut, and analyzed for stable C, N, and S isotopes to examine food web structure and anadromy. Preliminary results indicate that the presence of sea-run Arctic char may impact the ?<sup>15</sup>N-determined trophic position and condition of sympatric populations of lake trout <em>S. namaycush</em>. When stable S isotope results were applied to a two-source mixing model, marine food items accounted for 84-100% of the diet of mature, anadromous Arctic char. A semiquantitative assessment of char-mediated nutrient transport between marine and freshwater environments at Nauyuk Lake, Nunavut, indicated that masses of nutrients imported by char to freshwater systems are likely negligible in relation to ambient water chemistry. There was significant among-year variability in the magnitude and direction of nutrient transport, and the complex life history of anadromous Arctic char requires more research before detailed nutrient budgets can be calculated.
8
"Rotenone in Fisheries: Are the Rewards Worth the Risks?" In Rotenone in Fisheries: Are the Rewards Worth the Risks?, edited by Charles W. Thompson, Craig L. Clyde, Douglas K. Sakaguchi, and Leo D. Lentsch. American Fisheries Society, 2001. http://dx.doi.org/10.47886/9781888569339.ch10.
Анотація:
<em>Abstract.—</em>-An aspirator, was developed by the Utah Division of Wildlife Resources to mix rotenone slurry used to eradicate undesirable fish species from Strawberry Reservoir, Utah, in 1990. An aspirator was the best method that Utah has developed for mixing powdered rotenone into a slurry. Slurry characteristics were as good or better than those achieved by any other mixing technique tried. The system utilized a high pressure pump that forced water through the aspirator creating suction used to vacuum powdered rotenone from bulk bags (1,000 lb capacity). The powder and water combined inside the aspirator chamber forming a slurry. The slurry was discharged directly on to the reservoir surface or delivered into barge tanks from the aspirator nozzle. Rotenone loss in the form of dust was significantly reduced compared to other mixing techniques and there was limited exposure of the chemical to personnel. One person could operate the aspirator efficiently.
9
Krainoi, Apinya, Jobish Johns, Ekwipoo Kalkornsurapranee, and Yeampon Nakaramontri. "Carbon Nanotubes Reinforced Natural Rubber Composites." In Carbon Nanotubes - Redefining the World of Electronics [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95913.
Анотація:
Several advanced methods have been introduced to disperse CNTs in the NR matrix. Various aspects highlighted in this chapter include the mixing processes such as melt mixing and latex mixing methods. As well as, formations of functional groups on the surfaces of CNT using silane coupling agents (i.e., ex-situ and in-situ functionalization). Moreover, hybrid CNT are beneficial to achieve better electrical conductivity of NR/CNT composites. These efforts are aimed to reduce the percolation threshold concentration in the NR composites for application as conducting composites based on electrically insulating rubber matrix. Sensor application is developed based on conducting NR composites. NR composites showed changing of resistivity during elongation termed as piezoresistivity. The most commonly used rubber matrices such as NR, ENR and IR are mixed with a combination of CNT and CB fillers as hybrid filler. The presence of linkages in the ENR composites results in the least loss of conductivity during external strain. It is found that the conductivity becomes stable after 3000 cycles. This is found to be similar to the NR-CNT/CB composite, while a few cycles are needed for IR-CNT/CB owing to the higher filler agglomeration and poor filler-rubber interactions. This is attributed to the polar chemical interactions between ENR and the functional groups on the surfaces of CNT/CB.
10
Burch, William R., Gary E. Machlis, and Jo Ellen Force. "Introduction." In The Structure and Dynamics of Human Ecosystems. Yale University Press, 2017. http://dx.doi.org/10.12987/yale/9780300137033.003.0001.
Анотація:
This introductory chapter discusses how environmental scientists, managers, and other professionals need to intensify their search for cross-cultural models of resource systems that include the forces driving human desires. Socio-cultural variables as both cause and consequence of system change will need to be joined to the traditional biophysical concerns of the ecologist, forester, conservationist, range manager, park superintendent, and rural agriculturalist. Worldwide, disparate indicators of ecosystem stress abound. Some of these challenges include geochemical flux due to pollution, the accumulating inventory of toxic chemicals, a collapsing world fishery, biotic mixing, accelerating loss of coral reefs, desertification, and more. The chapter then introduces the Human Ecosystem Model (HEM) as a possible solution to these problems.
Тези доповідей конференцій з теми "Mixing losses":
1
Rose, Martin G., and Neil W. Harvey. "Turbomachinery Wakes: Differential Work and Mixing Losses." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-025.
Анотація:
In this paper the mixing of stator wakes in turbomachinery is considered. An extension is made to the existing model of Denton (1993), which addresses the effects of acceleration before mixing. Denton showed that if a total pressure wake was accelerated mixing loss diminished and vice versa. Here a total temperature wake is shown to exhibit a reverse trend. An attempt is also made to better understand the work transfer process between a stator wake and a rotor. The paper concentrates on axial turbines, but a brief look at compressors is included. It is argued that the freestream work is not the same as the wake work and the concept of ‘Differential Work’ is introduced. A simple steady velocity triangle based model is proposed to give an estimate of the ratio of wake work to freestream work (μ see later). The model is compared to an unsteady CFD result to offer some verification of the assumptions. It is concluded that the rotodynamic work process tends to reduce total pressure wake depths in turbines and compressors and therefore mixing losses. The mixing loss due to total temperature wakes is less strongly affected by the differential work process.
2
RIGGINS, D., and C. MCCLINTON. "Analysis of losses in supersonic mixing and reacting flows." In 27th Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1991. http://dx.doi.org/10.2514/6.1991-2266.
3
Schlüß, Daniel, and Christian Frey. "Mixing Losses in Steady and Unsteady Simulations of Turbomachinery Flows." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75524.
Анотація:
The aim of the present work is to facilitate insight into the modeling errors in the context of blade row coupling approaches which capture unsteady flow phenomena at different levels of detail. The focus is on RANS-based steady mixing plane computations as well as time domain and frequency domain unsteady computations. The concept of mixing loss is revisited to quantify the amount of unsteadiness in a flow field. Following an idea by Fritsch and Giles, we compute a second order approximation of the mixing losses which are generated at blade row interfaces. The resulting formula decomposes the entropy jump into contributions of circumferential and temporal fluctuations. The mathematical derivation, however, is based upon simpler arguments. It is shown that Fritsch and Giles’ main result can be extended to non-ideal gases. Moreover, the second order mixing loss formula is applied to time and frequency domain unsteady simulations. It is shown that an additional term has to be computed which accounts for the interaction of evanescent acoustic modes if the method is applied to unsteady flows. The methodology decomposes the overall mixing entropy into contributions of single perturbation types and harmonics. This may be used to assess whether unsteady flow phenomena of interest are adequately resolved and, in particular, to quantify the unsteadiness contained in the unresolved harmonics. A detailed investigation of the transonic IGV-rotor configuration of DLR’s Rig 250 compressor demonstrates the approach.
4
Pappu, K. R., and M. T. Schobeiri. "Optimization of Trailing Edge Ejection Mixing Losses: A Theoretical and Experimental Study." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-523.
Анотація:
The aerodynamic effects of trailing edge ejection on mixing losses downstream of cooled gas turbine blades were experimentally investigated and compared with an already existing one-dimensional theory by Schobeiri (1989). The significant parameters determining the mixing losses and therefore the efficiency of cooled blades are the ejection velocity ratio, the cooling mass flow ratio, the temperature ratio, the slot thickness ratio and the ejection flow angle. To cover a broad range of representative turbine blade geometry and flow deflections, a General Electric power generation gas turbine blade with high flow deflection and a NASA-turbine blade with intermediate flow deflection and different thickness distributions were experimentally investigated and compared with the existing theory. Comprehensive experimental investigations show that for the ejection velocity ratio μ = 1, the trailing edge ejection reduces the mixing losses downstream of the cooled gas turbine blade to a minimum which is in agreement with the theory. For the given cooling mass flow ratios that are dictated by the heat transfer requirements, optimum slot thickness to trailing edge thickness ratios are found, which correspond to the minimum mixing loss coefficients. The results allow the turbine aerodynamicist to minimize the mixing losses and to increase the efficiency of cooled gas turbine blades.
5
El-Dosoky, M. F., A. Rona, and J. P. Gostelow. "An Analytical Model for Over-Shroud Leakage Losses in a Shrouded Turbine Stage." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27786.
Анотація:
This study presents an analytical model that uses directly measurable flow quantities to predict the effects of leakage on shrouded turbine stage performance. The model displays good predictive ability for the mass leakage fraction, for the tip leakage and for the mixing losses. The model resolves the negative incidence angle induced by mixing the leakage flow with the main stream and predicts the increment in the total mixing loss coefficient at increasing injection angles. The effects of the labyrinth seal geometry, such as the tip gap width and the number of seals, on the associated leakage losses as well as on the turbine stage performance are adequately represented. Overall, the present model exhibits a good qualitative and quantitative agreement with comparative benchmark data. It is concluded that increasing the labyrinth through-flow resistance by increasing the number of fins leads to a decrement in the leakage flow and its adverse effects but the effectiveness of this reduction decreases as the number of fins increases by more than three. The mass leakage fraction, tip leakage loss coefficient and total mixing loss coefficient increase linearly as the sealing gap ratio increases. A conventional injection angle of 90° increases the total mixing loss by about 28% compared to injecting parallel to the main passage flow.
6
Praisner, T. J., J. P. Clark, T. C. Nash, M. J. Rice, and E. A. Grover. "Performance Impacts Due to Wake Mixing in Axial-Flow Turbomachinery." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90666.
Анотація:
One of the last loss mechanisms remaining to be quantified and correlated for inclusion in meanline predictive systems concerns the mixing of wakes across downstream airfoil rows. Here, we demonstrate that the unsteady losses incurred as turbomachinery wakes mix in downstream rows are a function of the velocity ratio across the downstream row as calculated in the frame of reference of wake generation. Analytical and computational results, compared to measurements of wakes mixing under variable free-stream velocity conditions, reveal that wake-loss modification is primarily a result of an inviscid dilation of the stream tubes that comprise the wake fluid. Further, simulations of wakes exposed to a range of turbomachinery-specific velocity ratios indicate that wake-loss augmentation caused by stream-tube dilation is significantly more pronounced than wake-loss reductions imparted by stream-tube contraction. It is demonstrated that wakes in turbines are dilated in the adjacent downstream row, whether it is a vane or a blade row, through a work extraction process that occurs in the wake-generation reference frame. Finally, comparisons between rig data and CFD simulations suggest that wake-mixing losses, enhanced by downstream rows, can contribute as much as 1.5 percent of lost efficiency in multistage low-pressure turbines.
7
Jackson, D. J., K. L. Lee, P. M. Ligrani, P. D. Johnson, and F. O. Soechting. "Transonic Aerodynamic Losses due to Turbine Airfoil, Suction Surface Film Cooling." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-260.
Анотація:
The effects of suction surface film cooling on aerodynamic losses are investigated using an experimental apparatus designed especially for this purpose. A symmetric airfoil with the same transonic Mach number distribution on both sides is employed. Mach numbers along the airfoil surface range from 0.4 to 1.24 and match values on the suction surface of airfoils from operating aeroengines. Film cooling holes are located on one side of the airfoil near the passage throat where the freestream Mach number is nominally 1.07. Round cylindrical, and conical diffused film cooling hole configurations are investigated with density ratios from 0.8 to 1.3 over a range of blowing ratios, momentum flux ratios, and Mach number ratios. Also included are discharge coefficients, local and integrated total pressure losses, downstream kinetic energy distributions, Mach number profiles, and n correlation for integral aerodynamic losses as they depend upon film cooling parameters. The contributions of mixing and shock waves to total pressure losses are separated and quantified. These results show that losses due to shock waves vary with blowing ratio as shock wave strength changes. Aerodynamic loss magnitudes due to mixing vary significantly with film cooling hole geometry, blowing ratio, Mach number ratio, and (in some situations) density ratio. Integrated mixing losses from round cylindrical boles are three times higher than from conical diffused holes, when compared at the same blowing ratio. Such differences depend upon mixing losses just downstream of the airfoil as well as turbulent diffusion of streamwise momentum normal to the airfoil symmetry plane.
8
Lyall, M. Eric, Paul I. King, and Rolf Sondergaard. "Endwall Loss and Mixing Analysis of a High Lift Low Pressure Turbine Cascade." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68709.
Анотація:
A high lift LPT profile designated L2A is used as a test bed for studying the origin of endwall mixing loss and the role of vortical structures in loss development. It is shown analytically and experimentally that the mixing forces within the endwall wake can be decoupled into either mean flow or turbulent forces, and can be further classified as either reversible or irreversible. Among the irreversible forces, mean flow shear is negligible compared to turbulent shear, suggesting that turbulence dissipation is the dominant cause of loss generation. As a result, the mean flow components of the vortical structures do not generate significant mixing losses. Rather than mixing effects, the mean flow of the vortices cause the suction surface boundary layer to separate inside the passage, thereby generating the large low energy regions typical of endwall flows. Losses are generated as the low energy regions mix out. This vortex separation effect is demonstrated with an experiment using a profile fence and pressure surface modification near the endwall. The findings in this paper suggest that profile modifications near the endwall that suppress suction surface separation may provide loss reductions additive to those that weaken vortical structures, such as endwall contouring.
9
Popov, Alexander K., Sergey A. Myslivets, Thomas F. George, and Vladimir M. Shalaev. "Compensating Losses in Doped Negative-Index Metamaterials via Four-Wave Mixing and Quantum Control." In Frontiers in Optics. Washington, D.C.: OSA, 2007. http://dx.doi.org/10.1364/fio.2007.fwj4.
10
Young, J. B., and R. C. Wilcock. "Modelling the Air-Cooled Gas Turbine: Part 1 — General Thermodynamics." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0385.
Анотація:
This paper is Part I of a study concerned with developing a formal framework for modelling air-cooled gas turbine cycles and deals with basic thermodynamic issues. Such cycles involve gas mixtures with varying composition which must be modelled realistically. A possible approach is to define just two components, air and gas, the latter being the products of stoichiometric combustion of the fuel with air. If these components can be represented as ideal gases, the entropy increase due to compositional mixing, although a true exergy loss, can be ignored for the purpose of performance prediction. This provides considerable simplification. Consideration of three idealised simple cycles shows that the introduction of cooling with an associated thermal mixing loss does not necessarily result in a loss of cycle efficiency. This is no longer true when real gas properties and turbomachinery losses are included. The analysis clarifies the role of the cooling losses and shows the importance of assessing performance in the context of the complete cycle. There is a strong case for representing the cooling losses in terms of irreversible entropy production as this provides a formalised framework, clarifies the modelling difficulties and aids physical interpretation. Results are presented which show the effects on performance of varying cooling flowrates and cooling losses. A comparison between simple and reheat cycles highlights the rôle of the thermal mixing loss. Detailed modelling of the heat transfer and cooling losses is discussed in Part II of this paper.
Звіти організацій з теми "Mixing losses":
1
Deb, Robin, Paramita Mondal, and Ardavan Ardeshirilajimi. Bridge Decks: Mitigation of Cracking and Increased Durability—Materials Solution (Phase III). Illinois Center for Transportation, December 2020. http://dx.doi.org/10.36501/0197-9191/20-023.
Анотація:
Type K cement offers a lower slump than conventional concrete, even at a higher water-to-cement ratio. Therefore, a suitable chemical admixture should be added to the Type K concrete mix design at a feasible dosage to achieve and retain target slump. In this project, a compatibility study was performed for Type K concrete with commercially available water-reducing and air-entraining admixtures. Slump and air content losses were measured over a period of 60 minutes after mixing and a particular mid-range water-reducing admixture was found to retain slump effectively. Furthermore, no significant difference in admixture interaction between conventional and Type K concrete was observed. Another concern regarding the use of Type K concrete is that its higher water-to-cement ratio can potentially lead to higher permeability and durability issues. This study also explored the effectiveness of presoaked lightweight aggregates in providing extra water for Type K hydration without increasing the water-to-cement ratio. Permeability of concrete was measured to validate that the use of presoaked lightweight aggregates can lower water adsorption in Type K concrete, enhancing its durability. Extensive data analysis was performed to link the small-scale material test results with a structural test performed at Saint Louis University. A consistent relation was established in most cases, validating the effectiveness of both testing methods in understanding the performance of proposed shrinkage-mitigation strategies. Stress analysis was performed to rank the mitigation strategies. Type K incorporation is reported to be the most effective method for shrinkage-related crack mitigation among the mixes tested in this study. The second-best choice is the use of Type K in combination with either presoaked lightweight aggregates or shrinkage-reducing admixtures. All mitigation strategies tested in this work were proved to be significantly better than using no mitigation strategy.
2
Petrov, M. P., R. Bell, R. V. Budny, N. N. Gorelenkov, S. S. Medley, and S. J. ,. PPPL Zweben. Global Confinement, Sawtooth Mixing, and Stochastic Diffusion Ripple Loss of Fast ICRF-driven H+ Minority Ions in TFTR. Office of Scientific and Technical Information (OSTI), July 1998. http://dx.doi.org/10.2172/289897.
3
Singhvi, Punit, Javier García Mainieri, Hasan Ozer, and Brajendra Sharma. Rheology-Chemical Based Procedure to Evaluate Additives/Modifiers Used in Asphalt Binders for Performance Enhancements: Phase 2. Illinois Center for Transportation, June 2021. http://dx.doi.org/10.36501/0197-9191/21-020.
Анотація:
The increased use of softer binders in Illinois over the past decade is primarily attributed to the increased use of recycled materials in asphalt pavement construction. The shift in demand of using PG 58-28 over PG 64-22 has resulted in potential alternative methods to produce softer binders more economically using proprietary products. However, there are challenges in using these proprietary products for asphalt modification because of uncertainty in their long-term performance and significant variability in binder chemistry. The current SuperPave performance grading specification for asphalt binders is insufficient in differentiating binders produced from these modifiers. Therefore, the objective of this study is to evaluate the performance of various softener-type asphalt binder modifiers using a wide array of rheological and chemistry tests for their integration into the Illinois Department of Transportation’s material specifications. The small-strain rheological tests and their parameters allowed for consistent grouping of modified binders and can be used as surrogates to identify performing and nonperforming asphalt binders. A new parameter, Δ|G*|peak τ, was developed from the linear amplitude sweep test and showed potential to discriminate binders based on their large-strain behavior. Chemistry-based parameters were shown to track aging and formulation changes. The modifier sources were identified using fingerprint testing and were manifested in the modified binder chemical and compositional characteristics. The two sources of base binders blended with the modifiers governed the aging rate of the modified binders. Mixture performance testing using the Illinois Flexibility Index Test and the Hamburg Wheel-Track Test were consistent with the rheological and chemical findings, except for the glycol amine-based modified binder, which showed the worst cracking performance with the lowest flexibility index among the studied modifiers. This was contrary to its superior rheological performance, which may be attributed to lower thermal stability, resulting in high mass loss during mixing. According to the characterization of field-aged binders, laboratory aging of two pressurized aging vessel cycles or more may represent realistic field aging of 10 to 15 years at the pavement surface and is able to distinguish modified binders. Therefore, an extended aging method of two pressurized aging vessel cycles was recommended for modified binders. Two different testing suites were recommended for product approval protocol with preliminary thresholds for acceptable performance validated with field-aged data.