Letteratura scientifica selezionata sul tema "Couple orbital de rotation"
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Articoli di riviste sul tema "Couple orbital de rotation":
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Bolmont, E., F. Gallet, S. Mathis, C. Charbonnel, L. Amard e Y. Alibert. "Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in massive planets". Astronomy & Astrophysics 604 (agosto 2017): A113. http://dx.doi.org/10.1051/0004-6361/201730662.
Abstract (sommario):
Observations of hot-Jupiter exoplanets suggest that their orbital period distribution depends on the metallicity of the host stars. We investigate here whether the impact of the stellar metallicity on the evolution of the tidal dissipation inside the convective envelope of rotating stars and its resulting effect on the planetary migration might be a possible explanation for this observed statistical trend. We use a frequency-averaged tidal dissipation formalism coupled to an orbital evolution code and to rotating stellar evolution models in order to estimate the effect of a change of stellar metallicity on the evolution of close-in planets. We consider here two different stellar masses: 0.4 M⊙ and 1.0 M⊙ evolving from the early pre-main sequence phase up to the red-giant branch. We show that the metallicity of a star has a strong effect on the stellar parameters, which in turn strongly influence the tidal dissipation in the convective region. While on the pre-main sequence, the dissipation of a metal-poor Sun-like star is higher than the dissipation of a metal-rich Sun-like star; on the main sequence it is the opposite. However, for the 0.4 M⊙ star, the dependence of the dissipation with metallicity is much less visible. Using an orbital evolution model, we show that changing the metallicity leads to different orbital evolutions (e.g., planets migrate farther out from an initially fast-rotating metal-rich star). Using this model, we qualitatively reproduced the observational trends of the population of hot Jupiters with the metallicity of their host stars. However, more steps are needed to improve our model to try to quantitatively fit our results to the observations. Specifically, we need to improve the treatment of the rotation evolution in the orbital evolution model, and ultimately we need to consistently couple the orbital model to the stellar evolution model.
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Pezzotti, C., P. Eggenberger, G. Buldgen, G. Meynet, V. Bourrier e C. Mordasini. "Revisiting Kepler-444". Astronomy & Astrophysics 650 (giugno 2021): A108. http://dx.doi.org/10.1051/0004-6361/202039652.
Abstract (sommario):
Context. Kepler-444 is one of the oldest planetary systems known thus far. Its peculiar configuration consisting of five sub-Earth-sized planets orbiting the companion to a binary stellar system makes its early history puzzling. Moreover, observations of HI-Lyα variations raise many questions about the potential presence of escaping atmospheres today. Aims. We aim to study the orbital evolution of Kepler-444-d and Kepler-444-e and the impact of atmospheric evaporation on Kepler-444-e. Methods. Rotating stellar models of Kepler-444-A were computed with the Geneva stellar evolution code and coupled to an orbital evolution code, accounting for the effects of dynamical, equilibrium tides and atmospheric evaporation. The impacts of multiple stellar rotational histories and X-ray and extreme ultraviolet (XUV) luminosity evolutionary tracks are explored. Results. Using detailed rotating stellar models able to reproduce the rotation rate of Kepler-444-A, we find that its observed rotation rate is perfectly in line with what is expected for this old K0-type star, indicating that there is no reason for it to be exceptionally active as would be required to explain the observed HI-Lyα variations from a stellar origin. We show that given the low planetary mass (~0.03 M⊕) and relatively large orbital distance (~0.06 AU) of Kepler-444-d and e, dynamical tides negligibly affect their orbits, regardless of the stellar rotational history considered. We point out instead how remarkable the impact is of the stellar rotational history on the estimation of the lifetime mass loss for Kepler-444-e. We show that, even in the case of an extremely slow rotating star, it seems unlikely that such a planet could retain a fraction of the initial water-ice content if we assume that it formed with a Ganymede-like composition.
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Daley, Thomas M., e Dale Cox. "Orbital vibrator seismic source for simultaneous P‐ and S‐wave crosswell acquisition". GEOPHYSICS 66, n. 5 (settembre 2001): 1471–80. http://dx.doi.org/10.1190/1.1487092.
Abstract (sommario):
A recently developed borehole seismic source, the orbital vibrator, was successfully deployed in a crosswell survey in a fractured basalt aquifer. This seismic source uses a rotating eccentric mass to generate seismic energy. Source sweeps with clockwise and counter‐clockwise rotations are recorded at each source location. Because this source generates circularly polarized waves, unique processing algorithms are used to decompose the recordings into two equivalent linearly oscillating, orthogonally oriented seismic sources. The orbital vibrator therefore generates P‐ and S‐waves simultaneously for all azimuths. A coordinate rotation based on P‐wave particle motion is used to align the source components from various depths. In a field experiment, both P‐ and S‐wave arrivals were recorded using fluid‐coupled hydrophone sensors. The processed field data show clear separation of P‐ and S‐wave arrivals for in‐line and crossline source components, respectively. A tensor convolutional description of the decomposition process allows for extension to multicomponent sensors.
4
Lindh, Grant D., Taylor J. Mach e T. Daniel Crawford. "The optimized orbital coupled cluster doubles method and optical rotation". Chemical Physics 401 (giugno 2012): 125–29. http://dx.doi.org/10.1016/j.chemphys.2011.11.002.
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Li, Liang, e Yiqiu Mao. "On Dynamics of Double-Diffusive Convection in a Rotating Couple-Stress Fluid Layer". Mathematics 12, n. 7 (28 marzo 2024): 1017. http://dx.doi.org/10.3390/math12071017.
Abstract (sommario):
The current article focuses on the examination of nonlinear instability and dynamic transitions in a double-diffusive rotating couple-stress fluid layer. The analysis was based on the newly developed dynamic transition theory by T. Ma and S. Wang. Through a comprehensive linear spectrum analysis and investigation of the principle of exchange of stability (PES) as the thermal Rayleigh number crosses a threshold, the nonlinear orbital changes during the transition were rigorously elucidated utilizing reduction methods. For both single real and complex eigenvalue crossings, local pitch-fork and Hopf bifurcations were discovered, and directions of these bifurcations were identified along with transition types. Furthermore, nondimensional transition numbers that signify crucial factors during the transition were calculated and the orbital structures were illustrated. Numerical studies were performed to validate the theoretical results, revealing the relations between key parameters in the system and the types of transition. The findings indicated that the presence of couple stress and a slow diffusion rate of solvent and temperature led to smoother nonlinear transitions during convection.
6
Yeomans, D. K. "Cometary Orbital Dynamics and Astrometry". International Astronomical Union Colloquium 116, n. 1 (1989): 3–17. http://dx.doi.org/10.1017/s0252921100109613.
Abstract (sommario):
AbstractComets are the only large solar system bodies where nongravitational forces directly affect their dynamic motions. Their approach to within a few AU of the Sun initiates the vaporization of nucleus ices, and the resulting rocket-like effects either add to or subtract from the comet’s orbital energy; the sign of the energy change depends upon the comet’s rotation direction and its spin pole orientation. The cometary outgassing phenomena have generally been modeled by assuming a rapidly rotating nucleus of water ice that outgasses symmetrically with respect to perihelion. Although this nongravitational acceleration model has been quite successful in providing accurate orbits and ephemerides, several comets exhibit water production rates and visual light curves that are noticeably asymmetric with respect to perihelion. New asymmetric models are being developed that attempt to represent more closely the cometary outgassing phenomena. For the same comet, derived nongravitational parameters can differ widely, depending upon which model is used to fit the astrometric data. The uncertainties in the data and in the nongravitational acceleration model prevent realistic extrapolations of these objects’ motion beyond a few hundred years, particularly if close planetary encounters are involved. Accurate orbits, ephemerides and efforts to model the nongravitational effects ultimately depend upon the quality of the astrometric data. Using a combination of long-focus telescopes, charge coupled device (CCD) detectors, microdensitometer reductions and modern star catalogs, cometary astrometric data can be generated that are accurate to the sub arcsecond level. While occultation, spacecraft, and radar observations can provide powerful astrometric data when available, it is still the ground-based optical observations that must provide the vast majority of data for cometary astrometry in the foreseeable future.
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Gallet, F., E. Bolmont, J. Bouvier, S. Mathis e C. Charbonnel. "Planetary tidal interactions and the rotational evolution of low-mass stars". Astronomy & Astrophysics 619 (novembre 2018): A80. http://dx.doi.org/10.1051/0004-6361/201833576.
Abstract (sommario):
Context. The surface angular velocity evolution of low-mass stars is now globally understood and the main physical mechanisms involved in it are observationally quite constrained. However, while the general behaviour of these mechanisms is grasped, their theoretical description is still under ongoing work. This is the case, for instance, about the description of the physical process that extracts angular momentum from the radiative core, which could be described by several theoretical candidates. Additionally, recent observations showed anomalies in the rotation period distribution of open cluster, main sequence, early K-type stars that cannot be reproduced by current angular momentum evolution models. Aims. In this work, we study the parameter space of star-planet system’s configurations to investigate if including the tidal star-planet interaction in angular momentum evolution models could reproduce the anomalies of this rotation period distribution. Methods. To study this effect, we use a parametric angular momentum evolution model that allows for core-envelope decoupling and angular momentum extraction by magnetized stellar wind that we coupled to an orbital evolution code where we take into account the torque due to the tides raised on the star by the planet. We explore different stellar and planetary configurations (stellar mass from 0.5 to 1.0 M⊙ and planetary mass from 10 M⊕ to 13 Mjup) to study their effect on the planetary orbital and stellar rotational evolution. Results. The stellar angular momentum is the most impacted by the star-planet interaction when the planet is engulfed during the early main sequence phase. Thus, if a close-in Jupiter-mass planet is initially located at around 50% of the stellar corotation radius, a kink in the rotational period distribution opens around late and early K-type stars during the early main sequence phase. Conclusions. Tidal star-planet interactions can create a kink in the rotation period distribution of low-mass stars, which could possibly account for unexpected scatter seen in the rotational period distribution of young stellar clusters.
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Felker, Peter M. "Nuclear-orbital/configuration-interaction study of coupled translation-rotation states in (H2)2@C70". Journal of Chemical Physics 138, n. 4 (28 gennaio 2013): 044309. http://dx.doi.org/10.1063/1.4776262.
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Borre, C. C., D. Baade, A. Pigulski, D. Panoglou, A. Weiss, Th Rivinius, G. Handler et al. "Short-term variability and mass loss in Be stars". Astronomy & Astrophysics 635 (marzo 2020): A140. http://dx.doi.org/10.1051/0004-6361/201937062.
Abstract (sommario):
Context. Be stars are physically complex systems that continue to challenge theory to understand their rapid rotation, complex variability, and decretion disks. γ Cassiopeiae (γ Cas) is one such star but is even more curious because of its unexplained hard thermal X-ray emission. Aims. We aim to examine the optical variability of γ Cas and thereby to shed more light on its puzzling behaviour. Methods. We analysed 321 archival Hα spectra from 2006 to 2017 to search for frequencies corresponding to the 203.5 day orbit of the companion. Space photometry from the SMEI satellite from 2003 to 2011 and the BRITE-Constellation of nano-satellites from 2015 to 2019 were investigated in the period range from a couple of hours to a few days. Results. The orbital period of the companion of 203.5 days is confirmed with independent measurements from the structure of the Hα line emission. A strong blue versus red asymmetry in the amplitude distribution across the Hα emission line could hint at a spiral structure in the decretion disk. With the space photometry, the known frequency of 0.82 d−1 is confirmed in data from the early 2000s. A higher frequency of 2.48 d−1 is present in the data from 2015 to 2019 and possibly in the early 2000s as well. A third frequency at 1.25 d−1 is proposed to exist in both SMEI and BRITE data. Seemingly, only a non-radial pulsation interpretation can explain all three variations. The two higher frequencies are incompatible with rotation.
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Belokonov, I. V., I. A. Timbai, P. N. Nikolaev e U. M. Orazbaeva. "Analysis of SamSat-218D nanosatelite motion acording to trajectory measurements". VESTNIK of Samara University. Aerospace and Mechanical Engineering 18, n. 4 (21 gennaio 2020): 18–28. http://dx.doi.org/10.18287/2541-7533-2019-18-4-18-28.
Abstract (sommario):
The motion of the SamSat-218D nanosatellite is analyzed by trajectory measurements. Special features of nanosatellite behavior in low orbits were experimentally confirmed. These features are due to both the influence of the atmosphere and the nanosatellites’ inherent mass-inertia characteristics: the orbital lifetime of nanosatellites is shorter, whereas angular acceleration generated by the aerodynamic moment couple is much higher than that of satellites with large sizes and masses. Variation of the ballistic coefficient in time is estimated from known trajectory measurements and information on the average density of the atmosphere at the points of trajectory measurements. The ballistic coefficient of the SamSat-218D nanosatellite having the shape of a rectangular parallelepiped depends on the spatial angle of attack and the angle of proper rotation. The ratio of the maximum value of the ballistic coefficient to the minimum value is 4.75. This made it possible to evaluate the nature of possible motion relative to the nanosatellite center of mass by the behavior of the ballistic coefficient. The most probable motion relative to the center of mass of the SamSat-218D nanosatellite is the transient motion between different equilibrium positions, due to commensurate aerodynamic and gravitational moments and insignificant angular velocities.
Tesi sul tema "Couple orbital de rotation":
1
Guo, Zongxia. "Electrical and optical manipulation of exchange bias". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0204.
Abstract (sommario):
L'expansion rapide en termes d'échelle et de complexité des dispositifs électroniques pour les applications d'apprentissage automatique et d'intelligence artificielle actuelles engendre une demande considérable en nouvelles architectures. L'industrie est activement à la recherche de nouvelle génération de mémoires et de stockage capables d'offrir vitesse, densité, et une meilleure efficacité énergétique. Les mémoires non volatile magnétorésistive (MRAM), dont les états magnétiques permettent de stocker l'information suscitent un intérêt grandissant. Jusqu'à présent la direction d'aimantation de matériaux ferromagnétique définissaient l'état magnétique. Cependant, les matériaux antiferromagnétiques ne possédant quasiment pas d'aimantation sont intéressant puisqu'ils ne sont pas sensibles aux champs magnétiques externes. Cette caractéristique permet de minimiser l'influence d'interactions dipolaires entre des dispositifs adjacents, favorisant ainsi une intégration plus dense. De plus les matériaux antiferromagnétiques présentent une dynamique à haute fréquence allant jusqu'à la gamme des térahertz, ce qui ouvre théoriquement la possibilité de vitesses d'écriture plus élevées que les dispositifs ferromagnétiques. Toutefois, des dispositifs à aimantation nulle rendent la manipulation et la détection de l'état mémoire complexe par des méthodes classiques. Dans le cadre de cette thèse, nous avons démontré le renversement du couplage d'échange ou exchange bias dans des héterostructures ferromagnétique/antiferromagnétique au sein de jonctions magnétiques à tunnel à trois terminaux, parvenant ainsi à détecter électriquement une couche antiferromagnétique via une variation de magnétorésistance tunnel de 80 %, soit deux ordres de grandeur plus importantes que les résultats publiés précédemment. Ici, la configuration magnétique de la couche antiferromagnétique (IrMn) impacte la couche libre ferromagnétique de CoFeB. De plus, nous avons pu démontrer un retournement d'aimantation rapide dépendant de la polarité du courant, en 0,8 ns. Nous avons pu identifier deux mécanismes de basculement, à savoir le mode chauffage et le mode induit par le couple spin-orbite, en fonction de la largeur d'impulsion du courant. Le second cas est en accord avec des simulations numériques, suggérant que le couple spin-orbite généré par le Pt induit la précession de l'IrMn, tandis que le couplage d'échange à l'interface IrMn/CoFeB détermine la polarité de basculement de l'IrMn. De plus, dans des structures IrMn/CoGd, nous avons étudier le couplage d'échange perpendiculaire en variant les épaisseurs d'IrMn et les concentrations de CoGd. Nous avons pu démontrer dans une structure optimisée, le retournement du couplage d'échange avec une seule impulsion laser femtoseconde. Par ailleurs, nous avons analysé l'impact de la fluence laser et du nombre pulse laser sur l'évolution du couplage d'échange. Grace a des mesures pompe-sonde, nous avons pu démontrer le retournement du couplage d'échange en moins de 100 ps. Ces résultats ont pu être reproduit par des simulations atomistiques prenant en compte la structure des grains des films d'IrMn polycristallins et l'état amorphe des couches d'alliage de CoGd. L'IrMn montre une désaimantation plus rapide que les matériaux ferromagnétiques, chaque grain d'IrMn parvenant à se réaimanter en un état monodomaine en seulement 2 ps. En conclusion le couplage d'échange peut être manipuler grâce à un courant électrique ou une impulsion optique ultra brève sans champ magnétique appliqué et pour des dispositifs ayant une bonne stabilité thermique, ce qui en fait une solution intéressantes pour diverses applicationsThe rapid growth in scale and complexity of neural network architectures in today's machine learning and artificial intelligence applications is creating a significant demand for advanced hardware solutions. The semiconductor industry is actively seeking next-generation storage technologies that can offer improved speed, density, power consumption, and scalability. One such technology that shows great promise for high-performance data storage and processing is magnetoresistive random access memory (MRAM), which stores information in the magnetic state of materials. However, with the continuous requirement of high-density and ultrafast scenarios, antiferromagnet as the basic unit of MRAM shows obvious advantages. Antiferromagnetic materials have negligible macroscopic magnetism, making them highly robust to external magnetic fields. This property also allows for the absence of dipole interactions between adjacent bits, enabling higher-density integration. Additionally, antiferromagnetic materials exhibit high-frequency dynamics up to the terahertz range, theoretically enabling faster write speeds than ferromagnetic devices. However, such fully compensated magnetic moments make the magnetization state of the antiferromagnetic material difficult to manipulate and detect by traditional electrical methods. In this thesis, we demonstrate the antiferromagnetic exchange bias switching in three-terminal magnetic tunnel junctions and achieve electrical detection of antiferromagnetism by the tunnelling magnetoresistance with a ratio over 80%, which is two orders larger than previous methods. This is achieved by imprinting the state of antiferromagnet IrMn on the CoFeB free layer. We further realize current polarity-dependent switching, rather than current orientation-dependent switching of IrMn down to 0.8 ns. We identify two switching mechanisms, the heating mode and the spin-orbit torque driven mode, depending on the current pulse width. The latter case is supported by numerical simulations, which suggest that spin-orbit torque generated by Pt induces the precession of IrMn and exchange coupling at the IrMn/CoFeB interface determines the switching polarity of IrMn. Furthermore, to break the ferromagnetic and electrical write speed limit and further explore the antiferromagnetic switching speed, we experimentally realize exchange bias switching by a single femtosecond laser pulse. In the IrMn/CoGd structure, the perpendicular exchange bias is investigated for different IrMn thicknesses and CoGd concentrations. Using the optimized structure, the exchange bias was switched under a single femtosecond laser, and the dependence of the exchange bias variations with different laser fluence and pulse numbers was detailed investigated. The pump-probe time-resolved measurement is used to demonstrate the exchange bias switching time scale of less than 100 ps. The grain structure of polycrystalline IrMn films and the amorphous state of CoGd alloy layers are accurately described using atomistic simulations. The IrMn exhibits a faster demagnetization than ferromagnetic materials and each IrMn grain remagnetizing to a single-domain state in only 2 ps. In addition, the different grains of IrMn exhibit independent and stochastic probabilistic switching in the ultrafast time scale. The electrical and all-optical manipulation of exchange bias system allows ultrafast, field-free and energy-efficient control of antiferromagnet with high ordering temperature and thermal stability, making it highly suited to applications
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Urbina, Iglesias Laura Sofia. "Guidance and robust control methods for the approach phase between two orbital vehicles with coupling between translational and rotational motions". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30086/document.
Abstract (sommario):
Les techniques liées au vol en formation et aux opérations de proximité de satellites autonomes font partie des technologies opérationnelles spatiales les plus marquantes et les plus ambitieuses de ces dernières années. En particulier, cela nécessite la complète maitrise des phases de rendez-vous proche et de survol par un satellite actif avec un satellite, une station ou un débris passif. Le développement de systèmes GNC (Guidage Navigation Contrôle) associés performants et sûrs repose sur la connaissance d'un modèle dynamique réalisant un bon compromis entre faible complexité et prise en compte suffisante des principales caractéristiques dynamiques et cinématiques de ce type de systèmes. La première partie de cette thèse est consacrée au développement d'une modélisation unifiée de la dynamique relative couplée entre un satellite coopératif chasseur et un satellite cible non coopérative. En effet, lorsque deux satellites sont proches l'un de l'autre, ils ne peuvent plus être traités comme des masses ponctuelles, car leur forme et leur taille affectent le mouvement relatif entre les points de masse décentralisés, conduisant à un couplage des mouvements de translation et de rotation. Ce développement est abordé de manière progressive: le mouvement de translation relatif non linéaire est décrit sous hypothèses képlériennes dans le repère orbital de la cible ainsi que le modèle linéarisé associé. Ensuite, le modèle non linéaire d'attitude relative est présenté au moyen des paramètres d'Euler-Rodrigues. Enfin, le formalisme des quaternions duaux est utilisé afin d'obtenir le modèle relatif couplé en translation et en attitude. La phase de modélisation du mouvement relatif linéaire de translation a ainsi permis de mettre en évidence certaines transformations de coordonnées conduisant à une caractérisation intéressante des trajectoires périodiques du chasseur et ainsi de proposer un premier type de loi de contrôle de guidage pour la phase d'approche et de survol. Dans l'ensemble de notre travail, nous considérons un chasseur équipé de propulseurs chimiques et l'hypothèse classique des poussées impulsionnelles. Ce type de systèmes dynamiques conciliant dynamique continue et contrôle impulsionnel se définit naturellement comme une classe particulière de systèmes dynamiques hybrides. Plusieurs lois de contrôle hybrides sont alors proposées afin de stabiliser le chasseur sur une trajectoire de référence périodique proche de la cible. Les propriétés de stabilité et de convergence de ces différentes lois sont analysées et de nombreuses simulations numériques montrent les forces et les faiblesses de chaque contrôleur en termes d'indices de performance comme le temps de convergence, la consommation ainsi que des contraintes de sécurité. Dans un second temps, des contraintes opérationnelles supplémentaires (contraintes de visibilité par exemple) sont prises en considération en imposant une direction d'approche rectiligne (glideslope) au chasseur. Cette trajectoire impose au satellite chasseur de suivre une droite dans n'importe quelle direction du repère local reliant l'emplacement courant du chasseur à sa destination finale. Sous l'hypothèse de propulsion impulsionnelle, les résultats existant dans la littérature pour ce type d'approche ont été généralisés aux orbites elliptiques en identifiant une nouvelle formulation du problème comprenant des degrés de liberté utiles qui permettent de minimiser la consommation de carburant tout en contrôlant l'excursion de la trajectoire libre en dehors de la droite de glideslope en la confinant dans un couloir d'approche défini par l'utilisateur. La synthèse des lois de guidage ainsi obtenues repose sur la résolution de problèmes d'optimisation SDP dans le cas général ou linéaire pour les cas plus simples d'approche standards du type V-bar ou R-barThe techniques related to formation flying and proximity operations of autonomous satellites belong to the most significant and challenging operational space technologies of the last years. In particular, they require full mastery of the close-range rendezvous and observation phases by an active satellite with a passive satellite, station or debris. The development of efficient and safe associated GNC systems relies on the knowledge of a dynamic model that achieves a good trade-off between low complexity and sufficient inclusion of the main dynamic and kinematic characteristics of this type of systems.The first part of this thesis is devoted to the development of a unified modeling of the relative coupled dynamics between a cooperative chaser satellite and a non-cooperative target satellite. Indeed, when two satellites are close to each other, they can no longer be treated as point masses because their shape and size affect the relative motion between the decentralized points, leading to a translational-attitude motions coupling. This development is addressed in a progressive way: the relative nonlinear translational motion is described under Keplerian assumptions in the target's orbital reference frame, as well as the associated linearized model. Then, the nonlinear relative attitude model is presented by means of the Euler-Rodrigues parameters. Finally, the dual quaternion formalism is used to obtain the relative translational and attitude coupled model. The modeling phase concerning the linear relative translational motion has allowed us to highlight certain coordinates transformations leading to an interesting characterization of the chaser's periodic trajectories and thus, to propose a first type of control law for the close-phase rendezvous and observation phases.All along this work, we consider a chaser satellite equipped with chemical thrusters under the classical hypothesis of impulsive thrusts. This type of dynamic systems gathering continuous dynamics and impulsive control naturally belongs to a particular class of dynamical hybrid systems. Several hybrid control laws are then proposed in order to stabilize the chaser on a periodic reference trajectory close to the target. The stability and convergence properties of these different laws are analysed and several numerical simulations show the strengths and weaknesses of each controller in terms of performance indices such as convergence time, consumption and safety constraints. In a second step, additional operational constraints (line-of-sight constraints for example) are taken into account by imposing a rectilinear (glideslope) direction to the chaser. This trajectory requires the chaser satellite to follow a straight line in any direction of the local reference frame and connecting the current location of the chaser to its final destination. Under the impulsive propulsion assumptions, the results in the literature for this type of approach have been generalized to elliptic orbits by identifying a new formulation of the problem including useful degrees of freedom, which allow minimizing the fuel consumption while controlling the humps of the trajectory outside the glideslope line by enclosing it in a user-defined approach corridor. Guidance laws are therefore synthetized via the solution of an SDP optimisation problem in the general case and via a linear programming when considering standard cases like the V-bar or R-bar approaches
3
Alli, Soklni-Sita. "Modélisation et optimisation sur cycle d'une génératrice doublement saillante faible vitesse de rotation pour hydrolienne". Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4002/document.
Abstract (sommario):
Cette étude traite d’une machine doublement saillante à aimants permanents, utilisée en entraînement direct pour application hydrolienne. Dans un premier temps, différentes approches technologiques utilisées pour l’exploitation hydrolienne sont passées en revue. Ensuite, la génératrice est modélisée par approche circuit. Cette méthode permet de tenir compte de la saturation magnétique et de la variation d’entrefer, tout en offrant un compromis intéressant entre la précision des résultats et le temps de simulation. Le modèle de la DSPM est ensuite couplé avec son convertisseur. Un modèle thermique est également mis en place. Ce modèle est ensuite utilisé pour optimiser simultanément la denture de la DSPM et les paramètres de la commande afin de maximiser le couple et de réduire ses ondulations, importantes dans les machines à saillance. Les paramètres de commande sont également optimisés sur un cycle hydrolien. Le premier critère à minimiser sur cycle concerne les ondulations de couple. Les pertes Joule sont ensuite rajoutées comme second critère. Des fronts de Pareto sont alors déduits et analysés. Finalement, des essais à vide et en charge sur un prototype 2 kW, 50 tr/min ont permis de valider le modèle théorique développéThis study deals with a doubly salient permanent magnet machine, used in direct drive for tidal application. First, different technological approaches used for tidal power generation are reviewed. Then, the generator is modelled by circuit approach. This method allows for magnetic saturation and airgap variation to be taken into account, while offering an interesting compromise between the accuracy of the results and the simulation time. The DSPM model is then coupled with its converter. A thermal model is also implemented. This model is then used to optimize simultaneously the DSPM teeth and its control parameters in order to maximize the torque and reduce its ripples which are important in salient machines. The control parameters are also optimized on a tidal cycle. The first criterion to be minimized on cycle is the torque ripples. Joule losses are added as a second criterion and Pareto fronts are deduced and analyzed. Finally, tests at no-load and also at load operations on a prototype 2 kW, 50 rpm validate the theoretical model developed
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Szlabowicz, Wojciech. "Contribution au dimensionnement et à la réalisation d'actionneur piézoélectrique à rotation de mode fort couple pour applications aéronautiques". Toulouse, INPT, 2006. http://ethesis.inp-toulouse.fr/archive/00000337/.
Abstract (sommario):
La présente recherche s’inscrit dans le cadre de travaux sur les Commandes de Vol de Futur (marché COVAN) de la société AIRBUS France. Si l’intérêt potentiel des moteurs piézoélectriques dans les applications avions de fortes puissance a été précédemment démontré, l’objectif général de l’étude est maintenant de concrétiser sur le plan applicatif l’introduction de cette technologie. L'étude porte donc sur la conception, la réalisation et la caractérisation d'un actionneur piézoélectrique à rotation de mode à double rotor, ainsi que de son alimentation électronique dédiée, en vue d'une application pour Trim de palonnier. Les performances obtenues montrent l'intérêt de cette solution technologique vis-à-vis du couple massique obtenu d'environ 8 N. M/kg très prisé pour les applications embarquéesPresent research deals with the aim of work on the Future of Flight Control (Market COVAN) of the AIRBUS France company. If the potential interest of the piezoelectric motors in the high power aeronautic applications were previously shown, the general objective of the study is now to concretize in an operationg actuator the introduction of this technology. The study deals to the design, the realization and the characterization of a rotating-mode piezoelectric actuator with a double rotor, dedicated electronic power supply, with aim to the Trim application. The performances obtained show the interest of this technological solution because of the torque/mass ratio obtained approximately in the range 8 N. M/kg, witch is a very interesting parameter in the field of the embedded applications
5
Szlabowicz, Wojciech Nogarède Bertrand Rouchon Jean-François. "Contribution au dimensionnement et à la réalisation d'actionneur piézoélectrique à rotation de mode fort couple pour applications aéronautiques". Toulouse : INP Toulouse, 2006. http://ethesis.inp-toulouse.fr/archive/00000337.
6
Zhao, Hongming. "ETUDE EXPERIMENTALE DE LA PROPRIETE DE COUPLAGE SPIN-ORBITE DANS DES STRUCTURES SEMI-CONDUCTRICES DE BASSE DIMENSIONALITE". Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00595906.
Abstract (sommario):
Nous avons étudié les propriétés optiques et le couplage spin-orbite dans différentes structures semi-conductrices de basse dimension. Tout d'abord, la dynamique de spin dans des gaz d'électrons bidimensionnels d'une hétérostructure GaAs/AlGaAs (001) a été étudiée par la technique de rotation Kerr résolue en temps. Les résultats montrent que la durée de vie du spin dans le plan du puits est anisotrope et que la densité des électrons affecte fortement le couplage spin-orbite de type Rashba. Nous avons observé ensuite une grande anisotropie du facteur g de l'électron dans des puits quantiques GaAs/AlGaAs (001) asymétriques, et la dépendance en température de son amplitude a été mesurée. Deuxièmement, nous avons fait l'étude expérimentale du dédoublement du spin électronique dans le plan des puits GaN/AlGaN C(0001) à température ambiante. La mesure du courant de l'effet photo-galvanique circulaire montre clairement un dédoublement isotrope dans le plan du puits. Troisièmement, les premières mesures du facteur g dans des films minces de GaAsN à température ambiante a été faite par la technique de rotation Kerr résolue en temps. Elles montrent que le facteur g peut être modifié drastiquement par l'introduction d'une petite quantité d'azote dans GaAs. Enfin, les caractéristiques optiques de transitions indirectes dans des séries de nano-bâtonnets linéaire CdTe/CdSe/CdTe de taille et de forme variables ont été étudiées par photoluminescence stationnaire et résolue en temps. Nos résultats montrent le transfert progressif d'une transition optique directe (type I) au sein de CdSe vers une transition indirecte (type II) entre CdSe/CdTe à mesure que la longueur des nano-bâtonnets augmente.
7
Nelson, Michael R. Jr. "Ab initio molecular orbital studies: Rydberg states of H₄ barriers to internal rotation studies binding of CO₂ to carbonyl groups isoprene and ozone complexes". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30278.
8
Diemer, Franck. "Utilisation en rotation continue des instruments de préparation canalaire en nickel-titane : évaluation des contraintes". Toulouse 3, 2006. http://www.theses.fr/2006TOU30283.
Abstract (sommario):
The first part of this work exposes a bibliographical synthesis about properties of memory-shape alloys and the characteristics of the small electric motors. The second part is experimental. We compared the resistance of instruments characterized by different profiles. We measured the differences induced by profile and pitch length on stresses generated by endodontic instrument used in continuous rotation. Then we try to evaluate the conditions of disengaging of different electric motors and contra-angles. We finally use, with a torque control motor, a file with the tip maintained in a screw-locking device. These studies show the role of instrument profile. Regarding the safe use of files, it appears more effective to work on the instruments design than to use controlled torque motor which are far away from manufacturers’ specifications. The use of badly calibrated disengaging or coupled to reversed rotation is completely ineffective.
9
Chegroun, Nouara. "Etude numérique des actions hydrodynamiques sur une sphère en translation et rotation dans la gamme des nombres de Reynolds inferieurs à 50". Vandoeuvre-les-Nancy, INPL, 1992. http://www.theses.fr/1992INPL122N.
Abstract (sommario):
Dans le but de déterminer les coefficients de trainée, de portance et de couple d'une sphère animée d'un mouvement de translation et de rotation simultanées, on propose une résolution numérique des équations de Navier-Stokes au moyen d'une méthode de correction de pression appliquée à un maillage non uniforme construit sur des coordonnées sphériques. L'étude est limitée au régime stationnaire, dans le domaine des nombres de Reynolds inferieurs à 50, qui sont ceux que l'on rencontre le plus fréquemment en mécanique des suspensions. Les résultats obtenus apportent des informations originales, complétant utilement les rares connaissances existantes dans cette gamme de nombres de Reynolds intermédiaires
10
Gomez, Chirinos José Luis. "Angle modeling of a rotating machine. Application to wind turbine surveillance". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI067/document.
Abstract (sommario):
Ce travail de recherche s'inscrit dans le cadre de la surveillance des machines tournantes en régime non stationnaire et plus particulièrement la détection des défauts de roulement. Il se focalise sur la modélisation et l'analyse des variations de la vitesse de rotation instantanée. Les modèles numériques développés s'appuient sur une approche originale dite " angulaire " qui introduit explicitement les degrés de rotation libres de la machine et permet de s'affranchir de condition de fonctionnement en régime stationnaire. Un modèle de roulement à billes à gorge profonde a été développé couplant les efforts de contact normaux et tangentiels grâce à l'introduction du phénomène de résistance au roulement. Ce couplage permet d'expliquer l'origine des fluctuations de vitesse de rotation en présence de défaut de bague extérieure, phénomènes constatés expérimentalement : la présence d'un défaut sur une bague modifie périodiquement le couple de frottement. La modélisation de la liaison par engrenages est plus classique, la problématique a été de s'assurer qu'elle était compatible avec l'approche angulaire utilisée dans ces travaux. Le couplage des éléments de roulement et d'engrenage dans un modèle simple a montré que la présence de défauts de roulement provoque des variations des efforts radiaux ce qui modifie les efforts d'engrènement et en conséquence perturbe également la vitesse de rotation. Un modèle simplifié d'une éolienne a été réalisé et utilisé pour tester et valider des indicateurs spectraux de surveillance en conditions de fonctionnement non stationnaires. La comparaison avec des mesures expérimentales issues d'une éolienne a montré la robustesse du modèle. Il peut donc être exploité comme un outil d'analyse phénoménologique et de test d'indicateurs de surveillance. Il a par exemple permis de montrer l'importance des conditions de fonctionnement (charge et vitesse) sur le niveau des indicateurs utilisés en surveillance. Si besoin, les développements proposés peuvent être étendus sans difficulté à des modèles plus complexes de roulements, d'engrènements et de structures d'accueil de ces éléments technologiquesThis work has been developed within the framework of non-stationary rotating machinery surveillance with emphasis on the detection of roller bearing defects. It focuses on the modeling and analysis of instantaneous angular speed variations. The numerical models developed are based on an ``angular" approach which introduces explicitly the machine's free body rotation degrees of freedom allowing simulations in non stationary operating conditions. A deep groove ball bearing model has been developed coupling tangential and normal forces by taking into account the rolling resistance phenomenon. This coupling allows to explain the origin of angular speed fluctuations in the presence of outer race roller bearing defects, phenomena that has been observed experimentally: a roller bearing defect periodically modifies the friction torque. The description of the gear mesh has been performed by means of a classic approach where the scientific issue has been to verify the compatibility with the angular modeling, cornerstone of this dissertation. Integration of the roller bearing and the gear modeling approaches into a simple mechanical architecture has shown that the presence of bearing defects provoking variations in the rolling element-races normal forces, modifies the gear mesh forces leading to perturbations of the angular speed. A simplified wind turbine model has been used for the test and validation of non stationary surveillance spectral indicators. The robustness of the model has been shown by means of a comparison with measurements performed on a wind turbine. It has allowed to show the importance of the operating conditions (load and speed), on the level of indicators used. This means the model may be used as a tool for phenomenological analyses as well as a device to test surveillance indicators. If needed, the approaches presented may be easily extended into more complex models of bearings, gears, casings and foundations
Libri sul tema "Couple orbital de rotation":
1
Buglia, James J. Direct computation of orbital sunrise or sunset event parameters. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1986.
2
Wigg, Alison. Molecular orbital studies of large molecules: Internal rotation in the monofluorobenaldehydes. Salford: University of Salford, 1989.
3
Mann, Peter. Introductory Rotational Dynamics. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198822370.003.0003.
Abstract (sommario):
This chapter discusses the importance of circular motion and rotations, whose applications to chemical systems are plentiful. Circular motion is the book’s first example of a special case of motion using the laws developed in previous chapters. The chapter begins with the basic definitions of circular motion; as uniform rotation around a principle axis is much easier to consider, it is the focus of this chapter and is used to develop some key ideas. The chapter discusses angular displacement, angular velocity, angular momentum, torque, rigid bodies, orbital and spin momenta, inertia tensors and non-inertial frames and explores fictitious forces as well as transformations in rotating frames.
4
Eriksson, Olle, Anders Bergman, Lars Bergqvist e Johan Hellsvik. Applications of Density Functional Theory. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198788669.003.0003.
Abstract (sommario):
In this chapter we give examples of how density functional theory describes some of the most basic magnetic properties of a material. This involves spin and orbital moments, Heisenberg exchange parameters and magnetic form factors. Relativistic effects couple spin and orbital space and make magnetic materials anisotropic, which means that the ground state magnetization is oriented parallel or perpendicular to high symmetry directions of the crystalline structure. We also illustrate how well density functional theory describes cohesive properties and how magnetism influence these properties. These examples serve to give a general picture of how well density functional theory, as described in the previous chapters, can reproduce relevant features of magnetic materials, as well as to illustrate that the onset of spin-polarization can have drastic influence on all properties of a material.
5
Valenzuela, S. O. Introduction. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0011.
Abstract (sommario):
This chapter begins with a definition of spin Hall effects, which are a group of phenomena that result from spin–orbit interaction. These phenomena link orbital motion to spin direction and act as a spin-dependent magnetic field. In its simplest form, an electrical current gives rise to a transverse spin current that induces spin accumulation at the boundaries of the sample, the direction of the spins being opposite at opposing boundaries. It can be intuitively understood by analogy with the Magnus effect, where a spinning ball in a fluid deviates from its straight path in a direction that depends on the sense of rotation. spin Hall effects can be associated with a variety of spin-orbit mechanisms, which can have intrinsic or extrinsic origin, and depend on the sample geometry, impurity band structure, and carrier density but do not require a magnetic field or any kind of magnetic order to occur.
6
Cao, Gang, e Lance DeLong. Physics of Spin-Orbit-Coupled Oxides. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780199602025.001.0001.
Abstract (sommario):
Prior to 2010, most research on the physics and chemistry of transition metal oxides was dominated by compounds of the 3d-transition elements such as Cr, Mn, Fe, Co, Ni, and Cu. These materials exhibited novel, important phenomena that include giant magnetoresistance in manganites, as well as high-temperature superconductivity in doped La2CuO4 and related cuprates. The discovery in 1994 of an exotic superconducting state in Sr2RuO4 shifted some interest toward ruthenates. Moreover, the realization in 2008 that a novel variant of the classic Mott metal-insulator transition was at play in Sr2IrO4 provided the impetus for a burgeoning group of studies of the influence of strong spin-orbit interactions in “heavy” (4d- and 5d-) transition-element oxides. This book reviews recent experimental and theoretical evidence that the physical and structural properties of 4d- and 5d-oxides are decisively influenced by strong spin-orbit interactions that compete or collaborate with comparable Coulomb, magnetic exchange, and crystalline electric field interactions. The combined effect leads to unusual ground states and magnetic frustration that are unique to this class of materials. Novel couplings between the orbital/lattice and spin degrees of freedom, which lead to unusual types of magnetic order and other exotic phenomena, challenge current theoretical models. Of particular interest are recent investigations of iridates and ruthenates focusing on strong spin-orbit interactions that couple the lattice and spin degrees of freedom.
Capitoli di libri sul tema "Couple orbital de rotation":
1
Malament, David B. "On Relative Orbital Rotation in Relativity Theory". In Revisiting the Foundations of Relativistic Physics, 175–90. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0111-3_8.
2
Kéchichian, Jean Albert. "Effect of Atmospheric Drag Perturbation on Circular Orbits: Atmosphere Rotation Considerations". In Orbital Relative Motion and Terminal Rendezvous, 171–246. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64657-8_5.
3
Lainey, V., e A. Vienne. "Rotation of Natural Shaped Satellites and Their Orbital Motion". In Modern Celestial Mechanics: From Theory to Applications, 407–10. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-017-2304-6_31.
4
Binder, Bernd. "Dynamic Localized Autonomous Chaotic Orbital Patterns from Rotation-Translation Sequences". In 14th Chaotic Modeling and Simulation International Conference, 45–54. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-96964-6_4.
5
Fukushima, Kenji, e Shi Pu. "Relativistic Decomposition of the Orbital and the Spin Angular Momentum in Chiral Physics and Feynman’s Angular Momentum Paradox". In Strongly Interacting Matter under Rotation, 381–96. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-71427-7_12.
6
Maugin, Gérard A. "C: From “Capillarity” to “Couple Stress (in Medium with Constrained Rotation)”". In Advanced Structured Materials, 37–56. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-2434-4_4.
7
Hussmann, Hauke, Gaël Choblet, Valéry Lainey, Dennis L. Matson, Christophe Sotin, Gabriel Tobie e Tim Van Hoolst. "Implications of Rotation, Orbital States, Energy Sources, and Heat Transport for Internal Processes in Icy Satellites". In Satellites of the Outer Solar System, 315–46. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-7439-6_12.
8
Bohra, Nafeesa, Hermann De Meer e Aftab A. Memon. "Analysing the Orbital Movement and Trajectory of LEO (Low Earth Orbit) Satellite Relative to Earth Rotation". In Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 1–11. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-04260-7_1.
9
Gaustad, Edwin S. "The Nature of True--and Useful-Virtue: From Edwards to Franklin". In Benjamin Franizlin, Jonathan Edwards, And The Representation Of American Culture, 42–57. Oxford University PressNew York, NY, 1993. http://dx.doi.org/10.1093/oso/9780195077759.003.0004.
Abstract (sommario):
Abstract Perry Miller’s unhappiness over the misinterpretation of his “From Edwards to Emerson” essay (as though he had argued “in some mystical pretension ... for a direct line of intellectual descent”) should warn one against the particular grammatical construction of the subtitle. Miller at least had the advantage of a good deal more “from-ness,” one century to another, in moving between Edwards and Emerson than between Edwards (b. 1703) and Franklin (b. 1706). Yet Franklin’s longevity does allow for some chronological movement, though of course the interest here is more than temporal tracing or pigeonholing, more-to quote Miller once more-than treating the history of ideas as some sort of “mail-order catalogue.” So let it be said that I do not argue for a direct line of intellectual descent but will attempt, rather, to enter the differing intellectual worlds of our two figures. However distinct these separate worlds were, it will also be argued that the orbits of those worlds moved in a common cosmos, sometimes in a parallel or overlapping rotation. And both men hoped to prevent wild eccentricity of orbital motion.
10
"Orbital Rotation". In The Dwarf, 102–16. University of Hawaii Press, 2017. http://dx.doi.org/10.1515/9780824864699-006.
Atti di convegni sul tema "Couple orbital de rotation":
1
Maråk, Rasmus, Emmanuel Blazquez e Pablo Gómez. "Trajectory Optimization of a Swarm Orbiting 67P/Churyumov-Gerasimenko Maximising Gravitational Signal". In ESA 12th International Conference on Guidance Navigation and Control and 9th International Conference on Astrodynamics Tools and Techniques. ESA, 2023. http://dx.doi.org/10.5270/esa-gnc-icatt-2023-057.
Abstract (sommario):
Proper modelling of the gravitational fields of irregular asteroids and comets is an essential yet difficult part of any spacecraft visit and flyby to these bodies. Accurate density representations provide crucial information, e.g., for proximity operations of spacecraft near such bodies which rely heavily on it to design safe and efficient trajectories. [2] Recently, so-called neural density fields [1] have emerged as a versatile tool that can provide an accurate description of the density distribution of a body’s mass, internal and external shape with few prior requirements. This representation has several advantages as it requires no prior information on the body, converges even inside the Brillouin sphere, and is extensible even to heterogeneous density distributions of the celestial bodies. [1,3] However, it remains an open question whether there are feasible, achievable trajectories that provide sufficient information, i.e. gravitational signal, to model the gravity and density field of an irregular body with high fidelity using neural density fields. For instance, a previous study demonstrated that the planned trajectory of the OSIRIS-REx spacecraft around Bennu produced a gravitational signal that proved to be too sparse for the task [4]. This difficulty could be circumvented using a distributed data acquisition and learning approach, where a swarm of spacecraft instead of a single one would work to acquire the gravity signal and learn a body’s density field. In this work, we explore maximising the gravitational signal in a hypothetical mission around the comet 67P/Churyumov-Gerasimenko by using a swarm of spacecraft. Sets of spacecraft trajectories are simultaneously optimised to maximise overall signal return while minimising propellant budget for orbital manoeuvres. This proves to be a challenging optimization problem due to the complex topology of 67P’s gravitational field and its sidereal rotation. [5] In contrast to a single spacecraft scenario, this mission context allows us to improve the acquisition of the gravitational signal through multiple, simultaneous relative observation angles. Orbit propagation is based on an open-source polyhedral gravity model [6] using a detailed mesh of 67P and takes the comet’s sidereal rotation into account. Trajectory optimization routines rely on the open-source pygmo framework maintained by ESA’s Advanced Concepts Team to formulate the problem as a constrained, multi-objective optimization problem. The developed code is designed independently of the celestial body of interest and provided online to allow follow-up studies with related models on other bodies. Constraints considered for this application include partial line of sight with the rest of the swarm, absence of collision with the comet, spacecraft power generation and telemetry. A parameter of particular interest for this study is the number of spacecraft constituting the swarm, in order to investigate the potential benefits and signal return thresholds when using a distributed approach. We compare results on different formation flying scenarios with varying complexity of the imposed constraints. Further, we consider heterogeneous measures of the gravitational signal characterised by different view angles and altitudes with respect to the celestial body. Additionally, we can directly correlate richness of the obtained dataset of trajectories to the duration of the mission. Based on a dataset of points and accelerations for the swarm after varying amounts of time, we investigate the training of a geodesyNet to model P67’s mass density field. We compare the obtained fidelity in detail with the established synthetic training using randomly sampled points as in the original work on geodesyNet [1]. Thus, we can directly relate the signal obtainable in a real mission scenario with an ideal one. Overall, this work takes the next step in bringing neural density fields to an onboard mission scenario, where they can be a useful and potent tool complementing existing approaches such as polyhedral or mascon models. In practice, the developed, open-source code can serve as a testbed to evaluate whether a hypothetical mission scenario can reasonably rely on geodesyNets and neural density fields. It also serves as a first step in investigating the potential of autonomously learning small-body gravitational fields in a distributed fashion. The tools used for this study are fully available online and designed to be extended to more general distributed learning applications with spacecraft swarms around small celestial bodies. References [1] Izzo, D. and Gómez, P., 2021. Geodesy of irregular small bodies via neural density fields: geodesyNets. arXiv preprint arXiv:2105.13031. [2] Leonard, J.M., Geeraert, J.L., Page, B.R., French, A.S., Antreasian, P.G., Adam, C.D., Wibben, D.R., Moreau, M.C. and Lauretta, D.S., 2019, August. OSIRIS-REx orbit determination performance during the navigation campaign. In 2019 AAS/AIAA Astrodynamics Specialist Conference (pp. 1-20). [3] Cui, Pingyuan, and Dong Qiao. "The present status and prospects in the research of orbital dynamics and control near small celestial bodies." Theoretical and Applied Mechanics Letters 4.1 (2014): 013013. [4] von Looz, M., Gómez, P. and Izzo, D., 2021. Study of the asteroid Bennu using geodesyANNs and Osiris-Rex data. arXiv preprint arXiv:2109.14427. [5] Keller, H.U., Mottola, S., Skorov, Y. and Jorda, L., 2015. The changing rotation period of comet 67P/Churyumov-Gerasimenko controlled by its activity. Astronomy & Astrophysics, 579, p.L5. [6] Schuhmacher, J. (2022) Efficient Polyhedral Gravity Modeling in Modern C++. Technical University of Munich.
2
Afanasjev, V. V. "Soliton polarization rotation in fiber lasers". In Nonlinear Guided Waves and Their Applications. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/nlgw.1995.nfa4.
Abstract (sommario):
Over the past few years there has been considerable research undertaken into the problem of soliton propagation in birefringent fibers [1-5]. It was found that solitons are stable against birefringence, i.e. soliton polarization components couple through cross-phase modulation and the two-component (vector) soliton propagates as a single unit [1]. Vector solitons have been observed numerically [1, 2, 4] and experimentally [3, 5].
3
Valverde, J., J. L. Escalona, J. Domi´nguez e E. Freire. "Stability and Dynamic Analysis of the SET (Short Electrodynamic Tether)". In ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/vib-48323.
Abstract (sommario):
Space-tethers are very slender and flexible structures that are deployed in space. In recent times space-tethers have been the object of numerous studies in the field of astronautics. One of such structures is the SET (Short Electrodynamic Tether). The distinguishing characteristic of the SET is that it orbits with the axis of smallest moment of inertia normal to the orbit plane. The SET is in continuous rotation around this same axis, which allows it to maintain the aforementioned operating position. In most other cases, space-tethers orbit within the orbit plane. The SET is not perfectly straight after deployment. This fact could make the rotation unstable from the structural point of view, as predicted by the linear study of unbalanced rotors (supercritical velocities). However, if non-linear terms in the elastic and internal damping forces are considered in the model (hysteresis causes instability) the resulting motion of the structure could remain bounded. This assertion was shown in a previous study by the authors, through dynamic simulations of the system. In order to confirm these results, the present paper studies the stability of the SET’s solutions. A modified Jeffcott model will be the object of this study. The paper will end with a comparison of the results obtained with those rendered by previous works.
4
Haselsteiner, Andreas F., Aljoscha Sander e Klaus-Dieter Thoben. "A Three Degrees of Freedom Vibration Model for a Partially Installed Wind Turbine". In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79081.
Abstract (sommario):
Abstract Most offshore wind turbines are installed using the so-called single blade installation procedure. This means that after the tower, nacelle, and hub are installed, the rotor blades are mounted individually. This process step is difficult and sometimes leads to delays because relative motions between the hub and rotor blade need to be small and predictable to enable the successful mounting of the blade. Previously published measurements showed that the tower vibrates in a motion where the nacelle moves in “orbits” that often change shape and axis direction. In this work, we present a simple vibration model that captures some characteristics of the tower dynamics. The model represents the tower and the nacelle as two planar rigid bodies that are connected with a torsional spring. It has three degrees of freedom: the first body’s motion in x- and y-direction and the second body’s rotation around the first body. An offset between the second body’s center of mass and its point of rotation couples the translation of the first body with the rotation of the second body. For some configurations of the parameters that describe mass distribution, stiffness, and geometry, the model produces motion similar to wind turbines during installation: orbits that change in shape and direction. These complex motions occur even without external forcing. For other configurations, however, the tower vibrates in a stationary orbit.
5
Huang, Lu, Yunfeng Jin e Yuqiang Jiang. "Ultrafast orbital rotation in optical trapping with a femtosecond laser". In Optical Trapping Applications. Washington, D.C.: OSA, 2017. http://dx.doi.org/10.1364/ota.2017.ots1d.5.
6
Anderson, Alexander Q., Elizabeth F. Strong, Sean C. Coburn, Gregory B. Rieker e Juliet T. Gopinath. "Dual Comb Ranging and Rotation Sensing with Orbital Angular Momentum". In CLEO: Science and Innovations. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_si.2022.sf2f.4.
Abstract (sommario):
We demonstrate a dual comb ranging system capable of simultaneously measuring the distance to a target and the transverse rotation rate of the target by preparing the probe comb with orbital angular momentum.
7
Matloff, Gregory L. "The Holographic Solar Photon Thruster (SPT) : A Low-Earth Orbit Solar Sail". In ASME 2003 International Solar Energy Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/isec2003-44059.
Abstract (sommario):
Atmospheric drag limits most solar sails to altitudes>1000 km. A two-sail variant, the Solar-Photon Thruster (SPT) , could be used in Low-Earth Orbit (LEO). An SPT has a fixed-orientation collector sail that focuses light against a smaller, adjustable thruster sail. Maintaining the collector surface parallel to the Earth minimizes SPT drag in LEO. To minimize solar-radiation back pressure towards Earth, the upper collector surface is non-reflective. The reflective lower collector surface directs light reflected and reradiated from the Earth against the thruster. Thruster orientation is adjusted in LEO to increase the orbital energy by the net radiation-pressure. Experiments reveal that holograms are tolerant to solar-wind radiation. SPTs with white-light holographic thrusters are useful in LEO because small thruster rotations produce greatly altered reflectivity. It may be possible to holographically combine SPT collector and thruster.
8
Maksimyak, Peter P., Oleg V. Angelsky, Elena Kurek e Andrew P. Maksimyak. "Comparison of the orbital and spin rotation of a dielectric particle". In Optical Trapping and Optical Micromanipulation XV, a cura di Kishan Dholakia e Gabriel C. Spalding. SPIE, 2018. http://dx.doi.org/10.1117/12.2320273.
9
Vuong, Luat T., Amiel A. Ishaaya, Taylor D. Grow, Alexander L. Gaeta, Eric R. Eliel e Gert t’Hooft. "Off-Axis Vortices and Polarization Rotation via Orbital Angular Momentum Exchange". In Conference on Coherence and Quantum Optics. Washington, D.C.: OSA, 2007. http://dx.doi.org/10.1364/cqo.2007.jwc11.
10
Zhang, Yahui, Domenico Bongiovanni, Shiqi Xia, Zhichan Hu, Daohong Song, Roberto Morandotti, Hrvoje Buljan e Zhigang Chen. "Photonic Higher-order Topological Orbital States and Nonlinearity-mediated Dynamical Rotation". In CLEO: QELS_Fundamental Science. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_qels.2022.ftu4j.3.
Abstract (sommario):
We experimentally demonstrate photonic higher-order topological orbital corner states in laser-written breathing Kagome lattices, unveiling their charaterisitic dipole-like mode distribution and dynamical rotation in presence of optical nonlinearity.