Bibliografie tematiche / Oscillations

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Letteratura scientifica selezionata sul tema "Oscillations"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 1 agosto 2024

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Articoli di riviste sul tema "Oscillations"

1

Xu, Jun, Zongjun Ning, Dong Li, Fanpeng Shi, Yuxiang Song e Yuzhi Yang. "An Investigation of the Loop Oscillations after a Solar Flare". Universe 10, n. 5 (29 aprile 2024): 201. http://dx.doi.org/10.3390/universe10050201.

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We study the loop oscillations after a solar flare on 19 January 2023, in the active region N11E40 3196, which is well observed by the SDO/AIA. After tracing the loop position and fitting, we find that the loop oscillations have a period between 3 and 9 min at various locations, such as from the leg to the top or from the inner to the outer loop. Their oscillating amplitudes decrease with time. Two loops display the position oscillation simultaneously with their brightness oscillation. After the analysis of the differential emission measure (DEM), we find that two of their loop position oscillations resulted from the plasma density fluctuation. Meanwhile, it is interesting that the brightness of these two position oscillations displays a typical period of about 4 min, similar to that of the position oscillation. This is possible due to both the plasma density and temperature fluctuation there. Our findings provide the physical clues for studying and understanding the mechanism of the loop position and brightness oscillations.
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Klimov, Alexandr V., e Akop V. Antonyan. "Research of features of oscillating process’ behavior in the nonlinear system of individual traction drive of an electrobus". Izvestiya MGTU MAMI 17, n. 1 (24 giugno 2023): 87–96. http://dx.doi.org/10.17816/2074-0530-115233.

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BACKGROUND: When a vehicle is in motion, self-oscillations which properties are dependent on slip rate in a contact patch may occur in the area of tire interaction with ground surface. Oscillations frequency will vary in dependence with value of wheel slip relative to ground surface. Soft self-oscillations are excited by variable set of initial conditions at full slip in traction and driven wheel rolling modes as well as in mixed braking mode with partial slip. Hard mode of self-oscillations occurs at full wheel slip in braking mode. These processes have a negative impact on the processes in electric drive and mechanical drivetrain reducing their efficiency and may cause damage of components. Oscillations in the system are excited by interaction forces of an elastic tire with ground surface featuring vertical oscillations due to elastic behavior of its interaction with road unevenness. AIMS: Research of features of oscillating process behavior in the nonlinear system of individual traction drive of an electrobus. METHODS: Simulation of self-oscillation excitation processes in the area of contact interaction of a wheel and road was carried out in the MATLAB/Simulink software package. RESULTS: The article features the results of simulation and experimental studies of self-oscillation excitation processes of the KAMAZ 6282 electrobus moving on asphalt-concrete surface. It was found that vertical wheel displacement when moving through unevenness lead to oscillating behavior of vertical reaction forces in contact patches and, as a consequence, to oscillating behavior of longitudinal reaction forces, torque and rotation velocity of the shaft of the traction electric motor of the individual drive. It was defined that tire oscillation frequency is 67 Hz that coincides with electric motor shaft rotation oscillation frequency and this value is the same for both experiment and simulation. CONCLUSIONS: Practical value of the study lies in ability of using the study results at development of self-oscillation processes exclusion algorithms as a part of vehicle control system.
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SHUKLA, P. K. "Amplification of neutrino oscillations by a density ripple in dense plasmas". Journal of Plasma Physics 77, n. 3 (21 gennaio 2011): 289–91. http://dx.doi.org/10.1017/s002237781000070x.

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AbstractIt is shown that a pre-existing electron density ripple in a dense plasma can excite electron neutrino oscillations. For our purposes, we use the dispersion relation for neutrino oscillations and derive the Mathieu equation for the propagation of neutrino oscillations in the presence of a spatially oscillating electron density ripple. The Mathieu equation predicts instability of neutrino oscillations. The criterion under which instability occurs is presented. Analytical expressions for the neutrino oscillation frequency and the growth rate are obtained. The possible relevance of our investigation to non-thermal neutrino oscillations in dense plasma environments (e.g. the supernovae, the core of white dwarf stars etc.) is briefly mentioned.
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Dolgopolov, S. I. "Mathematical simulation of hard excitation of cavitation self-oscillations in a liquid-propellant rocket engine feed system". Technical mechanics 2021, n. 1 (30 aprile 2021): 29–36. http://dx.doi.org/10.15407/itm2021.01.029.

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Hard self-oscillation excitation differs from soft excitation in that self-oscillations are set up only if the initial departure of an oscillating system from equilibrium is strong enough. Experimental studies of cavitation oscillations in hydraulic systems with cavitating pumps of liquid-propellant rocket engines ((LPREs) include works that describe hard excitation of cavitation oscillations. By mow, hard excitation regimes have not been explained theoretically, to let alone their mathematical simulation. This paper presents a mathematical model of hard excitation of cavitation oscillations in a LPRE feed system, which comprises a mathematical model of cavitation self-oscillations in a LPRE feed system that accounts for pump choking and an external disturbance model. A mechanism of hard excitation of cavitation oscillations in a LPRE feed system is proposed. It is well known that hard excitation of cavitation self-oscillations may take place in cases where the pump feed system is near the boundary of the cavitation self-oscillation region. In this case, the self-oscillation amplitudes are small, and they are limited only by one nonlinearity (cavity volume vs. pump inlet pressure and flow relationship). Under excitation of sufficient intensity, the pump inlet pressure and flow find themselves in the choking characteristic; this may be responsible for choking and developed cavitation self-oscillations, which remain of interrupted type and do not go into the initial small-amplitude oscillations even after excitation removal. A mathematical simulation of hard excitation of cavitation self-oscillations was conducted to determine the parameters of cavitation self-oscillations in a bench feed system of a test pump. The simulation results show that without an external disturbance the pump system exhibits small-amplitude self-oscillations. On an external disturbance, developed (interrupted) cavitation oscillations are set up in the system, which is in agreement with experimental data. The proposed mathematical model of hard excitation of cavitation self-oscillations in a LPRE feed system allows one to simulate a case observed in an experiment in which it was possible to eliminate cavitation self-oscillations by an external disturbance.
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Li, Xiuchen, Jie Li, Zhaohui Zheng, Jinni Deng, Yi Pan e Xiaobin Ding. "A self-oscillating gel system with complex dynamic behavior based on a time delay between the oscillations". Soft Matter 18, n. 3 (2022): 482–86. http://dx.doi.org/10.1039/d1sm01635k.

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A series of self-oscillating gels with different cross-linking densities are designed and fabricated. Due to the time delay between chemical and mechanical oscillation, they exhibit different oscillating behaviors. The disrupted mechanical oscillations tend to be regular and periodic under inhibited conditions.
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Li, Shubo, Chengxun Yuan, Iya P. Kurlyandskaya, V. I. Demidov, M. E. Koepke, Jingfeng Yao e Zhongxiang Zhou. "Measurements of fluctuating electron temperature and space potential in a magnetized plasma with a single magnetically insulated baffled probe (MIBP)". Plasma Sources Science and Technology 31, n. 3 (1 marzo 2022): 037001. http://dx.doi.org/10.1088/1361-6595/ac5228.

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Abstract A single magnetically insulated baffled probe (MIBP) was used to study the potential and electron temperature oscillations in a magnetized plasma. It was shown, that, although the MIBP cluster allows a more detailed study of such oscillations, the single MIBP may provide useful information about the oscillation amplitudes and, in some cases, cross-coherency and cross-phase. These quantities can characterize oscillations and distinguish co-oscillating plasma parameters in cases where the placing of a MIBP cluster in a plasma is difficult or impossible. For the reported plasma case, in which there are two types of oscillations, it is shown how to determine the maximum and minimum possible values of the electron temperature fluctuations. Detailed analysis showed that, in the studied plasma, there are two types of oscillations, both incoherent with each other.
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Hehner, Marc T., Davide Gatti, Marios Kotsonis e Jochen Kriegseis. "Effects of actuation mode on plasma-induced spanwise flow oscillations". Journal of Physics D: Applied Physics 55, n. 20 (22 febbraio 2022): 205203. http://dx.doi.org/10.1088/1361-6463/ac526b.

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Abstract Two different plasma actuation strategies for producing near-wall flow oscillations, namely the burst-modulation and beat-frequency mode, are characterized with planar particle image velocimetry in quiescent air. Both concepts are anticipated to work as non-mechanical surrogates of oscillating walls aimed at turbulent flow drag reduction, with the added benefit of no moving parts, as the fluid is purely manipulated by plasma-generated body forces. The current work builds upon established flow-control and proof-of-concept demonstrators, as such, delivering an in-depth characterization of cause and impact of the plasma-induced flow oscillations. Various operational parameter combinations (oscillation frequency, duty cycle and input body force) are investigated. A universal performance diagram that is valid for plasma-based oscillations, independent of the actuation concept is derived. Results show that selected combinations of body force application methods suffice to reproduce oscillating wall dynamics from experimental data. Accordingly, the outcomes of this work can be exploited to create enhanced actuation models for numerical simulations of plasma-induced flow oscillations, by considering the body force as a function of the oscillation phase. Furthermore, as an advantage over physically displaced walls, the exerted body force appears not to be hampered by resonances and therefore remains constant independent of the oscillation frequency. Hence, the effects of individual parameter changes on the plasma actuator performance and fluid response as well as strategies to avoid undesired effects can be determined.
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Shulaev, N. S., G. F. Efimova e A. Z. Abdullaev. "STUDY OF AN OSCILLATING CHARGE IN A DIPOLE-QUADRUPOLE SYSTEM". Petroleum Engineering 21, n. 1 (15 maggio 2023): 178–82. http://dx.doi.org/10.17122/ngdelo-2023-1-178-182.

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The solution of the problem of determining the magnitude of the component of the electric field intensity vector generated by an oscillating charge in a dipole-quadrupole system in a homogeneous medium is obtained. Two mutually perpendicular directions of charge oscillations in a cylindrical coordinate system are considered. From the analysis of the obtained dependences for the oscillation frequencies, it can be seen that in the first case, the frequency of «vertical» oscillations exceeds the frequency of «horizontal» oscillations. Knowing the maximum and minimum frequencies of the oscillating charge radiation spectrum, it is possible to calculate the molecular parameters. The analysis of the parameters of the radiation spectrum of a harmonically oscillating charge performing a non-relativistic motion can be used in the analysis of the electromagnetic radiation spectra of atoms and molecules in an excited state, as well as the parameters of the crystal lattice.
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Kohutova, P., e A. Popovas. "Excitation and evolution of coronal oscillations in self-consistent 3D radiative MHD simulations of the solar atmosphere". Astronomy & Astrophysics 647 (marzo 2021): A81. http://dx.doi.org/10.1051/0004-6361/202039491.

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Context. Solar coronal loops are commonly subject to oscillations. Observations of coronal oscillations are used to infer physical properties of the coronal plasma using coronal seismology. Aims. Excitation and evolution of oscillations in coronal loops is typically studied using highly idealised models of magnetic flux tubes. In order to improve our understanding of coronal oscillations, it is necessary to consider the effect of realistic magnetic field topology and evolution. Methods. We study excitation and evolution of coronal oscillations in three-dimensional (3D) self-consistent simulations of solar atmosphere spanning from the convection zone to the solar corona using the radiation-magnetohydrodynamic (MHD) code Bifrost. We use forward-modelled extreme-ultraviolet emission and 3D tracing of magnetic field to analyse the oscillatory behaviour of individual magnetic loops. We further analyse the evolution of individual plasma velocity components along the loops using wavelet power spectra to capture changes in the oscillation periods. Results. Various types of oscillations commonly observed in the corona are present in the simulation. We detect standing oscillations in both transverse and longitudinal velocity components, including higher-order oscillation harmonics. We also show that self-consistent simulations reproduce the existence of two distinct regimes of transverse coronal oscillations: rapidly decaying oscillations triggered by impulsive events and sustained small-scale oscillations showing no observable damping. No harmonic drivers are detected at the footpoints of oscillating loops. Conclusions. Coronal loop oscillations are abundant in self-consistent 3D MHD simulations of the solar atmosphere. The dynamic evolution and variability of individual magnetic loops suggest that we need to re-evaluate our models of monolithic and static coronal loops with constant lengths in favour of more realistic models.
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W. Hussein, Mohammed, e Kadhim A. Al-Asadi. "Synchronous Impact of the North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI( Poles on Temperature and Rain Over Iraq". Israa University Journal for Applied Science 7, n. 1 (1 ottobre 2023): 290–302. http://dx.doi.org/10.52865/exzs7896.

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Background: This study is an attempt to analyze the correlation of the impact of the North Atlantic Oscillation( NAO )and Southern Oscillation Index( SOI ) on the climate of Iraq. Method: This has been conducted based on the highest and lowest recorded values of the mentioned oscillations. The values of temperature and rain for the stations of Mosul, Baghdad, Rutba, Basrah and for a major climatic cycle from 1950-2018 were also relied upon. On the statistical analytical approach to find the correlation relationship between the studied oscillations and depending on the Pearson Correlation Coefficient. Results: The results brought to light that there is a strong and statistically significant correlation between the oscillations. The time series of oscillations were also analyzed during the fall season, due to the absence of a single effect of oscillations on the studied elements. Therefore, the analysis of the simultaneous behavior of oscillations on the climatic elements during the autumn was relied upon. In the meantime, four cases of simultaneous behavior for selected years of the study were found, recording the highest oscillations’ values. Such four cases were compared with the values of the elements for those years. Conclusion: It became clear from the four cases that there are two cases that show a regular behavior of the influence, as it became clear when the poles are NAO +, SOI - and vice versa that the climatic elements are affected more clearly with the oscillation's indicators and that the climate of Iraq has become more affected by the oscillations.
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Tesi sul tema "Oscillations"

1

Kuzovkov, Vladimir, Guntars Zvejnieks, Olaf Kortlüke e Niessen Wolfgang von. "Forced oscillations in self-oscillating surface reaction models". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195406.

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Kuzovkov, Vladimir, Guntars Zvejnieks, Olaf Kortlüke e Niessen Wolfgang von. "Forced oscillations in self-oscillating surface reaction models". Diffusion fundamentals 2 (2005) 27, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14357.

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Andes, Derek. "Orbital oscillations". Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/919.

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Fraser, Geoffrey Alan. "Nonradial oscillations in Spica". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24667.

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The absorption line profiles of Spica (α Virginis, HD116658, B1.5IV, m=0.97) show features, at about the 1% level, moving from the blue wavelengths towards the red wavelengths. A series of spectra were taken, at the 1.22 m telescope at the Dominion Astrophysical Observatory on three nights in April, 1982 and two nights in April, 1984, to study these moving features. As Spica is a member of a binary system, the effect of the secondary had to be removed from the observations. This was done by subtracting a template spectrum which had been scaled, broadened and shifted to match the secondary, from each observation. The required shifts were determined using the orbital elements on blended nights and using the Fahlman-Glaspy small-shifts technique on unblended nights. An average of all the spectra was then subtracted from each observation. The resulting series of residuals clearly show the motion of the features seen in the line profiles. The acceleration of the features was estimated to be between 0.0055 and 0.0068 kms⁻². Assuming the features are due to nonradial oscillations, this acceleration corresponds to waves moving slowly, about 5 to 20 kms⁻¹, in a prograde direction. The angular frequency of the oscillations, after accounting for the effects of rotation, would be about 3.4X10⁻⁵ rads⁻¹. A computer model that produces line profiles, under the assumption of a single nonradial oscillation, was used to produce profiles for comparison with observations. Using an [formula omitted]=8 and m=-8 mode, an intrinsic frequency of 3.4X10⁻⁵ rads⁻¹ and a stellar rotation rate of 190 kms⁻¹, the model produced profiles similar to those observed. The change in the model profiles with time was also similar to that observed.
Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Rangavajhula, Krishna C. "Nonstationary oscillations through bifurcations". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23875.pdf.

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Reid, Giles Adrian. "Neutrino Oscillations in Astrophysics". Thesis, University of Canterbury. Physics and Astronomy, 2010. http://hdl.handle.net/10092/4935.

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A survey of the theory of neutrino oscillations in dense matter and neutrino backgrounds is presented. We discuss collective neutrino systems using the gyroscopic pendulum analogy and describe the motion that results from self-induced parametric resonances. The effects of dense matter on the flavour oscillations of neutrinos are also detailed. This theory is applied to the case of continuous supernova neutrino spectra and explanations of the spectral swapping behaviour seen in numerical studies are summarized. The results of numerical simulations of supernova oscillations in turbulent supernova backgrounds are presented and discussed. We study the motion of two example supernova neutrino spectra and examine the differences in the dynamics and flavour evolution that results from adding turbulent fluctuations to the supernova matter background. We also investigate the effect that fluctuations in the neutrino density can have on the oscillation behaviour. We find that in general the final neutrino spectra emerging from the inner supernova regions are quite robust to fluctuations in the backgrounds in our model, while the intermediate dynamics can be very strongly altered. Some significant changes in the final spectra are also found to occur when the neutrino background density fluctuations are large. We give a detailed review of the resonant matter effects that determine the survival probabilities of atmospheric muon neutrinos. The differences between various Earth density models are described, and these models are then used to predict the flux of muon-type neutrino events in the Deep Core extension to the IceCube detector. We use recent results from the detector collaboration and build on previous work which considered the sensitivity of the detector to the mass hierarchy, and show that uncertainties in the Earth's density can have a significant influence on the event rates.
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Pennequin, Denis. "Contrôle optimal et oscillations". Paris 1, 2000. http://www.theses.fr/2000PA010061.

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Dans cette thèse, nous nous sommes intéressés au problème du Contrôle Optimal des oscillations et à quelques applications économiques. Tout d'abord, on a mis en forme le formalisme de Percival liant une fonction quasi-périodique (=q. P. ) à sa génératrice sur le tore, avec un lien se comportant bien au niveau différentiel. Une étude du cas à paramètre, nécessaire pour traiter des équations autonomes, permet d'obtenir un théorème d'isomorphisme entre l'espace des fonctions presque- périodiques ( =p. P. ) à paramètres et un espace de fonctions p. P. à valeurs dans un Banach. Relativement au formalisme de Percival, nous introduisons des espaces du type de Sobolev où nous retrouvons l'absence de compacité, mais où l'étude ne nécessite pas d'hypothèses diophantiennes contrairement aux considérations plus géométriques de ces problèmes. Le formalisme de Percival transforme la recherche des solutions q. P. D'une équation différentielle en la recherche de solutions p. P. D'une E. D. P. Une notion de solution faible est introduite et comparée à l'usuelle, et l'on obtient pour celle-ci un théorème d'existence. L'absence de compacité implique une obligation de développer de nouvelles techniques, y compris dans les méthodes de régularisation, et l'on présente pour cela une nouvelle technique. Le cas discret est également traité (existence et structure), après avoir comparé différentes notions de suites p. P, courantes dans la littérature. On étudie alors les problèmes quasi-périodiques ; pour des problèmes autonomes linéaires-concaves, on démontre l'équivalence des problèmes p. P. , périodiques et statiques. Dans le cadre non nécessairement autonome, on obtient des théorèmes d'existence et de conditions nécessaire étendant ceux de Da-Prato et Ichikawa. Enfin, des applications économiques sont fournies.
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Todd, Thomas. "Robust oscillations in cells". Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685923.

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Oscillating chemical signals in cells play an essential role in biological processes. Understanding how to produce reliable oscillators using cellular machinery is useful for genetic engineering and is a key goal of synthetic biology. Motivated by an analysis of the robustness of a biological oscillator found in the cell cycle, a new technique is developed to evaluate the robustness of nonlinear models of oscillating genetic networks. This technique has been embedded in a software framework called INTRON which can be used by biologists seeking to design robust genetic oscillators or to understand the robustness of existing models. A set of case studies are presented in which INTRON is used to analyse the robustness of genetic oscillators.
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Amon, Axelle. "Dynamique temporelle des oscillateurs paramétriques optiques continus : oscillations multimodes, oscillations en rafales et chaos". Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2003. http://tel.archives-ouvertes.fr/tel-00004477.

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Les oscillateurs paramétriques optiques (OPO) continus sont des sources de lumière cohérente largement accordables reposant sur l'interaction paramétrique de trois champs dans un cristal non-linéaire. Leur utilité est aussi bien liée à cette accordabilité (spectroscopie) qu'aux propriétés quantiques propres au système (génération d'états comprimés, photons jumeaux). D'autre part, en tant que systèmes non-linéaires, les OPO sont susceptibles de présenter une grande richesse de phénomènes dynamiques temporels et spatio-temporels. Nous présentons une étude expérimentale, théorique et numérique de différentes instabilités temporelles présentées par les intensités des champs à la sortie de la cavité de notre OPO. Nous caractérisons des oscillations de fréquence de 1 à 300MHz dont nous montrons expérimentalement qu'elles ont pour origine l'interaction entre plusieurs modes transverses. Ces oscillations rapides peuvent être couplées à des oscillations plus lentes d'origine thermique, menant à l'apparition d'instabilités du type oscillations en rafales. Un développement perturbatif multi-échelle permet d'obtenir des solutions analytiques pour les champs une fois les oscillations rapides moyennées. Nous avons d'autre part observé ce qui est à notre connaissance la première observation expérimentale de chaos déterministe dans ce système. Enfin nos travaux expérimentaux et théoriques ont permis d'améliorer notre compréhension de la sélection de modes dans les OPO.
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Schwabedal, Justus Tilmann Caspar. "Phase dynamics of irregular oscillations". Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2011/5011/.

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In der vorliegenden Dissertation wird eine Beschreibung der Phasendynamik irregulärer Oszillationen und deren Wechselwirkungen vorgestellt. Hierbei werden chaotische und stochastische Oszillationen autonomer dissipativer Systeme betrachtet. Für eine Phasenbeschreibung stochastischer Oszillationen müssen zum einen unterschiedliche Werte der Phase zueinander in Beziehung gesetzt werden, um ihre Dynamik unabhängig von der gewählten Parametrisierung der Oszillation beschreiben zu können. Zum anderen müssen für stochastische und chaotische Oszillationen diejenigen Systemzustände identifiziert werden, die sich in der gleichen Phase befinden. Im Rahmen dieser Dissertation werden die Werte der Phase über eine gemittelte Phasengeschwindigkeitsfunktion miteinander in Beziehung gesetzt. Für stochastische Oszillationen sind jedoch verschiedene Definitionen der mittleren Geschwindigkeit möglich. Um die Unterschiede der Geschwindigkeitsdefinitionen besser zu verstehen, werden auf ihrer Basis effektive deterministische Modelle der Oszillationen konstruiert. Hierbei zeigt sich, dass die Modelle unterschiedliche Oszillationseigenschaften, wie z. B. die mittlere Frequenz oder die invariante Wahrscheinlichkeitsverteilung, nachahmen. Je nach Anwendung stellt die effektive Phasengeschwindigkeitsfunktion eines speziellen Modells eine zweckmäßige Phasenbeziehung her. Wie anhand einfacher Beispiele erklärt wird, kann so die Theorie der effektiven Phasendynamik auch kontinuierlich und pulsartig wechselwirkende stochastische Oszillationen beschreiben. Weiterhin wird ein Kriterium für die invariante Identifikation von Zuständen gleicher Phase irregulärer Oszillationen zu sogenannten generalisierten Isophasen beschrieben: Die Zustände einer solchen Isophase sollen in ihrer dynamischen Entwicklung ununterscheidbar werden. Für stochastische Oszillationen wird dieses Kriterium in einem mittleren Sinne interpretiert. Wie anhand von Beispielen demonstriert wird, lassen sich so verschiedene Typen stochastischer Oszillationen in einheitlicher Weise auf eine stochastische Phasendynamik reduzieren. Mit Hilfe eines numerischen Algorithmus zur Schätzung der Isophasen aus Daten wird die Anwendbarkeit der Theorie anhand eines Signals regelmäßiger Atmung gezeigt. Weiterhin zeigt sich, dass das Kriterium der Phasenidentifikation für chaotische Oszillationen nur approximativ erfüllt werden kann. Anhand des Rössleroszillators wird der tiefgreifende Zusammenhang zwischen approximativen Isophasen, chaotischer Phasendiffusion und instabilen periodischen Orbits dargelegt. Gemeinsam ermöglichen die Theorien der effektiven Phasendynamik und der generalisierten Isophasen eine umfassende und einheitliche Phasenbeschreibung irregulärer Oszillationen.
Many natural systems embedded in a complex surrounding show irregular oscillatory dynamics. The oscillations can be parameterized by a phase variable in order to obtain a simplified theoretical description of the dynamics. Importantly, a phase description can be easily extended to describe the interactions of the system with its surrounding. It is desirable to define an invariant phase that is independent of the observable or the arbitrary parameterization, in order to make, for example, the phase characteristics obtained from different experiments comparable. In this thesis, we present an invariant phase description of irregular oscillations and their interactions with the surrounding. The description is applicable to stochastic and chaotic irregular oscillations of autonomous dissipative systems. For this it is necessary to interrelate different phase values in order to allow for a parameterization-independent phase definition. On the other hand, a criterion is needed, that invariantly identifies the system states that are in the same phase. To allow for a parameterization-independent definition of phase, we interrelate different phase values by the phase velocity. However, the treatment of stochastic oscillations is complicated by the fact that different definitions of average velocity are possible. For a better understanding of their differences, we analyse effective deterministic phase models of the oscillations based upon the different velocity definitions. Dependent on the application, a certain effective velocity is suitable for a parameterization-independent phase description. In this way, continuous as well pulse-like interactions of stochastic oscillations can be described, as it is demonstrated with simple examples. On the other hand, an invariant criterion of identification is proposed that generalizes the concept of standard (Winfree) isophases. System states of the same phase are identified to belong to the same generalized isophase using the following invariant criterion: All states of an isophase shall become indistinguishable in the course of time. The criterion is interpreted in an average sense for stochastic oscillations. It allows for a unified treatment of different types of stochastic oscillations. Using a numerical estimation algorithm of isophases, the applicability of the theory is demonstrated by a signal of regular human respiration. For chaotic oscillations, generalized isophases can only be obtained up to a certain approximation. The intimate relationship between these approximate isophase, chaotic phase diffusion, and unstable periodic orbits is explained with the example of the chaotic roes oscillator. Together, the concept of generalized isophases and the effective phase theory allow for a unified, and invariant phase description of stochastic and chaotic irregular oscillations.
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Libri sul tema "Oscillations"

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Suekane, Fumihiko. Quantum Oscillations. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70527-5.

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Suekane, Fumihiko. Neutrino Oscillations. Tokyo: Springer Japan, 2015. http://dx.doi.org/10.1007/978-4-431-55462-2.

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Kovacic, Ivana. Nonlinear Oscillations. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53172-0.

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Nayfeh, Ali Hasan. Nonlinear oscillations. New York: Wiley, 1995.

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5

Saker, Samir. Oscillation theory of dynamic equations on time scales: Second and third orders. Saarbrücken, Germany: LAP Lambert Academic Publishing, 2010.

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Sukharev, I︠U︡ I. Wave oscillations in colloid oxyhydrates. Stafa-Zuerich, Switzerland: Trans Tech Publications, 2010.

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Rogers, Graham. Power System Oscillations. Boston, MA: Springer US, 2000.

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Françoise, Jean-Pierre. Oscillations en biologie. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/3-540-37670-4.

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Rabinovich, M. I., e D. I. Trubetskov. Oscillations and Waves. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1033-1.

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Fitzpatrick, Richard. Oscillations and Waves. Second edition. | Boca Raton, FL : CRC Press, Taylor & Francis: CRC Press, 2018. http://dx.doi.org/10.1201/9781351063104.

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Capitoli di libri sul tema "Oscillations"

1

Arnold, V. I. "Oscillations". In Mathematical Methods of Classical Mechanics, 98–122. New York, NY: Springer New York, 1989. http://dx.doi.org/10.1007/978-1-4757-2063-1_5.

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Kuehn, Christian. "Oscillations". In Applied Mathematical Sciences, 397–430. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-12316-5_13.

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Kamal, Ahmad A. "Oscillations". In 1000 Solved Problems in Classical Physics, 235–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11943-9_6.

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4

Kronauer, Richard E. "Oscillations". In Handbook of Applied Mathematics, 697–746. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-1423-3_13.

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Stix, Michael. "Oscillations". In Astronomy and Astrophysics Library, 181–235. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-642-56042-2_5.

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Lifshits, M. A. "Oscillations". In Gaussian Random Functions, 53–67. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-015-8474-6_7.

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Timberlake, Todd Keene, e J. Wilson Mixon. "Oscillations". In Undergraduate Lecture Notes in Physics, 85–123. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4939-3207-8_4.

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Papachristou, Costas J. "Oscillations". In Introduction to Mechanics of Particles and Systems, 69–81. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-54271-9_5.

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Woodhouse, Nicholas M. J. "Oscillations". In Springer Undergraduate Mathematics Series, 147–60. London: Springer London, 2009. http://dx.doi.org/10.1007/978-1-84882-816-2_6.

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Ilie, Carolina C., Zachariah S. Schrecengost e Elina M. van Kempen. "Oscillations". In Classical Mechanics, 115–42. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003365709-5.

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Atti di convegni sul tema "Oscillations"

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Richards, George A., e Michael C. Janus. "Characterization of Oscillations During Premix Gas Turbine Combustion". 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-244.

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The use of premix combustion in stationary gas turbines can produce very low levels of NOx emissions. This benefit is widely recognized, but turbine developers routinely encounter problems with combustion oscillations during the testing of new pre mix combustors. Because of the associated pressure fluctuations, combustion oscillations must be eliminated in a final combustor design. Eliminating these oscillations is often time-consuming and costly because there is no single approach to solve an oscillation problem. Previous investigations of combustion stability have focused on rocket applications, industrial furnaces, and some aeroengine gas turbines. Comparatively little published data is available for premised combustion at conditions typical of an industrial gas turbine. In this paper, we report experimental observations of oscillations produced by a fuel nozzle typical of industrial gas turbines. Tests are conducted in a specially designed combustor, capable of providing the acoustic feedback needed to study oscillations. Tests results are presented for pressures up to 10 atmospheres, and with inlet air temperatures to 588 K (600 F) burning natural gas fuel. Based on theoretical considerations, it is expected that oscillations can be characterized by a nozzle reference velocity, with operating pressure playing a smaller role. This expectation is compared to observed data, showing both the benefits and limitations of characterizing the combustor oscillating behavior in terms of a reference velocity rather than other engine operating parameters. This approach to characterizing oscillations is then used to evaluate how geometric changes to the fuel nozzle will affect the boundary between stable and oscillating combustion.
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Kerenyi, K., S. Hillisch, H. Drobir e T. Staubli. "Flow Visualization of Oscillating Rectangular Prisms Arranged in Arrays and in Isolation". In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0549.

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Abstract This study examines the flow around an isolated rectangular prism as well as around and through an array of equidistant bars. These prisms are excited to oscillate by the flow for certain experimental parameters due to a lightly damped suspension. The experiments with suspension allowing oscillations with mechanically uncoupled, orthogonal degrees of freedom are described, as is the hydrogen bubble technique employed for visualization. A first interpretation of flow images is given starting with the stationary, single bar at various incidence angles of the flow. In a next step the oscillating isolated bar is discussed followed by arrays of five (non-oscillating) and three bars (oscillating). Special focus is put on the influence of the bar spacing and its influence on the excitation of oscillations. It is demonstrated that oscillation can be avoided by appropriately choosing the spacing.
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Paine, Garth. "Oscillations". In CHI'16: CHI Conference on Human Factors in Computing Systems. New York, NY, USA: ACM, 2016. http://dx.doi.org/10.1145/2851581.2891083.

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Rupasinghe, B. W. H. A., e U. D. Annakkage. "Identifying the presence of forced oscillations using oscillation signatures". In 2017 IEEE International Conference on Industrial and Information Systems (ICIIS). IEEE, 2017. http://dx.doi.org/10.1109/iciinfs.2017.8300376.

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Li, Xiaopeng, Xiangxi Duan, Fuchuan Hao, Ling Yu, Siyu Xiong, Jiuyuan Song e Ling Fu. "An Estimation Algorithm for Oscillation Frequency under Power Oscillations". In 2021 3rd Asia Energy and Electrical Engineering Symposium (AEEES). IEEE, 2021. http://dx.doi.org/10.1109/aeees51875.2021.9402978.

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Tamura, Tetsuro, e Yoshiaki Itoh. "Numerical Study on Aeroelastic Instability of a Rectangular Cylinder in Heaving Oscillations". In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0061.

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Abstract The unsteady three-dimensional flows around a forced-oscillating or freely oscillating rectangular cylinder are numerically simulated by means of the direct finite difference method without any turbulence model. We discuss the accuracy of the present method for prediction of unsteady aerodynamic forces and responses to various dynamic properties. First we examine the aerodynamic forces in case of forced oscillation with D/B = 2 of a rectangular cylinder through the comparison with experiments. Also, in order to understand fundamental behaviors of unstable oscillations of a rectangular cylinder, which is elastically mounted in heaving mode in uniform flow, the effect of various dynamic parameters such as mass ratio, damping ratio or the Scruton number, on aeroelastic instabilities is individually investigated.
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Kwong, Sze-Keung, e Amnon Yariv. "Bistable oscillations with a passive phase conjugator". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.thu3.

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When a passive phase conjugate mirror (PPCM) is conjugating an incident beam, a phase conjugate oscillation can be obtained by placing a mirror near to the PPCM. By placing an additional mirror adjacent to the first mirror, two oscillations can be observed. If we consider these two oscillations as two states of the system, the system exhibits interesting bistable behavior: the presence of one oscillation will prevent the other oscillation building up and vice versa. The system will remain in that state unless it is being disturbed, for example, blocking the oscillation by a piece of paper, then the system switches to the other state and remains in that state even after that piece of paper is removed. The switching between states can also be controlled by an external control beam. A theoretical model based on the threshold of oscillation is proposed. This device has potential application in bistable switches and associative memories.
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Yoshida, T., e T. Watanabe. "Numerical Simulations of Two-Dimensional Incompressible Flows Over Cavities and Their Control". In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37410.

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We investigate numerically self-sustained oscillating flows over open cavities. The incompressible Navier-Stokes equations are solved using finite difference method for two-dimensional cavities with an upstream laminar boundary layer. A series of simulations are performed for a variety of cavity length to depth ratio. The results show mode switchings among nonoscillations, mode II and mode III oscillations. Variation of Strouhal number is in good agreement with available experimental data. The results of flow fields in the cavity reveal the relationship between the cavity shear layer oscillation modes and recirculating vortices in the cavity. We also demonstrate that oscillations are suppressed by our control method using moving bottom wall.
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Kabiraj, Lipika, e R. I. Sujith. "Dynamics of Thermoacoustic Oscillations Leading to Lean Flame Blowout". In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68696.

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Lean flame blowout induced by thermoacoustic oscillations is a serious problem faced by the power and propulsion industry. We analyze a prototypical thermoacoustic system through systematic bifurcation analysis and find that starting from a steady state, this system exhibits successive bifurcations resulting in complex nonlinear oscillation states, eventually leading to flame blowout. To understand the observed bifurcations, we analyze the oscillation states using nonlinear time series analysis, particularly through the representation of pressure oscillations on a reconstructed phase space. Prior to flame blowout, a bursting phenomenon is observed in pressure oscillations. These burst oscillations are found to exhibit similarities with the phenomenon known as intermittency in the dynamical systems theory. This investigation based on nonlinear analysis of experimentally acquired data from a thermoacoustic system sheds light on how thermoacoustic oscillations lead to flame blowout.
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Lima, Roberta, e Rubens Sampaio. "Stick-slip oscillations or couple-decouple oscillations?" In DINAME2019. ABCM, 2019. http://dx.doi.org/10.26678/abcm.diname2019.din2019-0070.

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Rapporti di organizzazioni sul tema "Oscillations"

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Shadwick, B. A., e P. J. Morrison. On neutral plasma oscillations. Office of Scientific and Technical Information (OSTI), giugno 1993. http://dx.doi.org/10.2172/10180029.

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Loreti, F. N., e A. B. Balantekin. Neutrino oscillations in noisy media. Office of Scientific and Technical Information (OSTI), maggio 1994. http://dx.doi.org/10.2172/10166926.

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Janus, M. C., e G. A. Richards. A model for premixed combustion oscillations. Office of Scientific and Technical Information (OSTI), marzo 1996. http://dx.doi.org/10.2172/379049.

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Connolly, Roger. Decoherence of Betatron Oscillations in RHIC. Office of Scientific and Technical Information (OSTI), gennaio 1998. http://dx.doi.org/10.2172/1119243.

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Himmel, Alexander I. Antineutrino Oscillations in the Atmospheric Sector. Office of Scientific and Technical Information (OSTI), maggio 2011. http://dx.doi.org/10.2172/1015386.

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Berman, G. P., D. K. Campbell, E. N. Bulgakov e I. V. Krive. Quantum chaos in Aharonov-Bohm oscillations. Office of Scientific and Technical Information (OSTI), ottobre 1995. http://dx.doi.org/10.2172/119976.

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Friedland, Alexander. Collective neutrino oscillations in a supernova. Office of Scientific and Technical Information (OSTI), maggio 2013. http://dx.doi.org/10.2172/1078368.

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Avram, Florin, e Murrad S. Taqqu. Probability Bounds for M-Skorohod Oscillations. Fort Belvoir, VA: Defense Technical Information Center, dicembre 1986. http://dx.doi.org/10.21236/ada187981.

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Carroll III, Thomas Joseph. Three-Flavor Neutrino Oscillations with MINOS+. Office of Scientific and Technical Information (OSTI), gennaio 2019. http://dx.doi.org/10.2172/1576527.

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Ko, Kwok. Spurious Oscillations in High Power Klystrons. Office of Scientific and Technical Information (OSTI), giugno 2003. http://dx.doi.org/10.2172/813234.

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