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Articoli di riviste sul tema "Rotating field"

Autore: Grafiati

Pubblicato: 16 settembre 2023

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1

Shibahashi, H., e M. Takata. "Pulsation of Rotating Magnetic Stars". International Astronomical Union Colloquium 139 (1993): 134. http://dx.doi.org/10.1017/s0252921100117117.

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Recently, one of the rapidly oscillating Ap stars, HR 3831, has been found to have an equally split frequency septuplet, though its oscillation seems to be essentially an axisymmetric dipole mode with respect to the magnetic axis which is oblique to the rotation axis (Kurtz et al. 1992; Kurtz 1992). In order to explain this fine structure, we investigate oscillations of obliquely rotating magnetic stars by taking account of the perturbations due to the magnetic fields and the rotation. We suppose that the star is rigidly rotating and that the magnetic field is a dipole field and its axis is oblique to the rotation axis. We treat the effects of the rotation and of the magnetic field as perturbations. In doing so, we suppose that the rotation of the star is slow enough so that the effect of the rotation on oscillations is smaller than that of the magnetic field.

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Miguel, M. C., e J. M. Rubı́. "Rotating Magnetic Field-Induced Rotations of Magnetic Holes". Journal of Colloid and Interface Science 172, n. 1 (giugno 1995): 214–21. http://dx.doi.org/10.1006/jcis.1995.1245.

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Reiners, Ansgar. "Magnetic Fields in Low-Mass Stars: An Overview of Observational Biases". Proceedings of the International Astronomical Union 9, S302 (agosto 2013): 156–63. http://dx.doi.org/10.1017/s1743921314001963.

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AbstractStellar magnetic dynamos are driven by rotation, rapidly rotating stars produce stronger magnetic fields than slowly rotating stars do. The Zeeman effect is the most important indicator of magnetic fields, but Zeeman broadening must be disentangled from other broadening mechanisms, mainly rotation. The relations between rotation and magnetic field generation, between Doppler and Zeeman line broadening, and between rotation, stellar radius, and angular momentum evolution introduce several observational biases that affect our picture of stellar magnetism. In this overview, a few of these relations are explicitly shown, and the currently known distribution of field measurements is presented.

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Co, Raymond T., Keisuke Harigaya e Aaron Pierce. "Cosmic perturbations from a rotating field". Journal of Cosmology and Astroparticle Physics 2022, n. 10 (1 ottobre 2022): 037. http://dx.doi.org/10.1088/1475-7516/2022/10/037.

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Abstract Complex scalar fields charged under approximate U(1) symmetries appear in well-motivated extensions of the Standard Model. One example is the field that contains the QCD axion field associated with the Peccei-Quinn symmetry; others include flat directions in supersymmetric theories with baryon, lepton, or flavor charges. These fields may take on large values and rotate in field space in the early universe. The relevant approximate U(1) symmetry ensures that the angular direction of the complex field is light during inflation and that the rotation is thermodynamically stable and is long-lived. These properties allow rotating complex scalar fields to naturally serve as curvatons and explain the observed perturbations of the universe. The scenario imprints non-Gaussianity in the curvature perturbations, likely at a level detectable in future large scale structure observations. The rotation can also explain the baryon asymmetry of the universe without producing excessive isocurvature perturbations.

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Guo, Hao, Hyeon-Jung Kim e Sang-Young Kim. "Research on Hydrogen Production by Water Electrolysis Using a Rotating Magnetic Field". Energies 16, n. 1 (21 dicembre 2022): 86. http://dx.doi.org/10.3390/en16010086.

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In this paper, the effect of rotating magnetic fields on hydrogen generation from water electrolysis is analyzed, aiming to provide a research reference for hydrogen production and improving hydrogen production efficiency. The electrolytic environment is formed by alkaline solutions and special electrolytic cells. The two electrolytic cells are connected to each other in the form of several pipes. The ring magnets are used to surround the pipes and rotate the magnets so that the pipes move relative to the magnets within the ring magnetic field area. Experimentally, the electrolysis reaction of an alkaline solution was studied by using a rotating magnetic field, and the effect of magnetic field rotation speed on the electrolysis reaction was analyzed using detected voltage data. The experimental phenomenon showed that the faster the rotation speed of the rotating magnetic field, the faster the production speed of hydrogen gas.

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Matos, Tonatiuh, e Darío Núñez. "Rotating scalar field wormhole". Classical and Quantum Gravity 23, n. 13 (12 giugno 2006): 4485–95. http://dx.doi.org/10.1088/0264-9381/23/13/012.

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Диканский, Ю. И., М. А. Беджанян, А. А. Колесникова, А. Ю. Гора e А. В. Чернышев. "Динамические эффекты в магнитной жидкости с микрокаплями концентрированной фазы во вращающемся магнитном поле". Журнал технической физики 89, n. 3 (2019): 373. http://dx.doi.org/10.21883/jtf.2019.03.47171.242-18.

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AbstractVariation in the shape of microdrops of a highly concentrated magnetic colloid resulting from phase separation in a magnetic fluid has been studied. It has been found that even weak magnetic fields (such as those comparable to the geomagnetic field) substantially influence the geometry and behavior of microdrops. Different configurations of microdrops in a rotating magnetic field have been considered. The occurrence of a rotation moment that acts on a macrodrop of a magnetic fluid in a rotating magnetic field has been shown. The rotation moment is due to the rotation of concentrated phase microdrops inside the macrodrop. The macroscopic rotation frequency of a drop’s surface as a function of the applied magnetic field frequency and strength has been measured.

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Vargas-Rodríguez, H., A. Gallegos, M. A. Muñiz-Torres, H. C. Rosu e P. J. Domínguez. "Relativistic Rotating Electromagnetic Fields". Advances in High Energy Physics 2020 (29 dicembre 2020): 1–17. http://dx.doi.org/10.1155/2020/9084046.

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In this work, we consider axially symmetric stationary electromagnetic fields in the framework of special relativity. These fields have an angular momentum density in the reference frame at rest with respect to the axis of symmetry; their Poynting vector form closed integral lines around the symmetry axis. In order to describe the state of motion of the electromagnetic field, two sets of observers are introduced: the inertial set, whose members are at rest with the symmetry axis; and the noninertial set, whose members are rotating around the symmetry axis. The rotating observers measure no Poynting vector, and they are considered as comoving with the electromagnetic field. Using explicit calculations in the covariant 3 + 1 splitting formalism, the velocity field of the rotating observers is determined and interpreted as that of the electromagnetic field. The considerations of the rotating observers split in two cases, for pure fields and impure fields, respectively. Moreover, in each case, each family of rotating observers splits in two subcases, due to regions where the electromagnetic field rotates with the speed of light. These regions are generalizations of the light cylinders found around magnetized neutron stars. In both cases, we give the explicit expressions for the corresponding velocity fields. Several examples of relevance in astrophysics and cosmology are presented, such as the rotating point magnetic dipoles and a superposition of a Coulomb electric field with the field of a point magnetic dipole.

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Watterson, Peter A. "Analytical solutions for the current driven by a rotating magnetic field in a spherical plasma". Journal of Plasma Physics 46, n. 2 (ottobre 1991): 271–98. http://dx.doi.org/10.1017/s0022377800016111.

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The steady currents driven in a spherical plasma by a rotating magnetic field via the Hall effect are studied analytically. The total field is shown to be symmetric across the origin. Integral relationships are obtained between Ohmic dissipation, angular momentum and the oscillating axial current density. The topology of the sum of a Hill's vortex field and a rotating field is documented. Analytical solutions for the driven current are obtained by expansion for the limits corresponding to small rotation frequency, to small number density, to large rotating-field magnitude, to small resistivity, and to small rotating-field magnitude combined with very small resistivity. The latter solution, relevant to the reactor limit, indicates that, with control of the vertical field magnitude, an MHD equilibrium can be generated with total current any fraction of the currentcorresponding to synchronous rotation of the electrons. Oscillating currents sufficient to drive the synchronous current are determined.

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Ayadi, Badreddine, Fatih Selimefendigil, Faisal Alresheedi, Lioua Kolsi, Walid Aich e Lotfi Ben Said. "Jet Impingement Cooling of a Rotating Hot Circular Cylinder with Hybrid Nanofluid under Multiple Magnetic Field Effects". Mathematics 9, n. 21 (24 ottobre 2021): 2697. http://dx.doi.org/10.3390/math9212697.

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The cooling performance of jet impinging hybrid nanofluid on a rotating hot circular cylinder was numerically assessed under the effects of multiple magnetic fields via finite element method. The numerical study was conducted for different values of Reynolds number (100≤Re≤300), rotational Reynolds number (0≤Rew≤800), lower and upper domain magnetic field strength (0≤Ha≤20), size of the rotating cylinder (2 w ≤r≤ 6 w) and distance between the jets (6 w ≤ H ≤ 16 w). In the presence of rotation at the highest speed, the Nu value was increased by about 5% when Re was increased from Re = 100 to Re = 300. This value was 48.5% for the configuration with the motionless cylinder. However, the rotations of the cylinder resulted in significant heat transfer enhancements in the absence or presence of magnetic field effects in the upper domain. At Ha1 = 0, the average Nu rose by about 175%, and the value was 249% at Ha1 = 20 when cases with the cylinder rotating at the highest speed were compared to the motionless cylinder case. When magnetic field strengths of the upper and lower domains are reduced, the average Nu decreases. The size of the cylinder is influential on the flow dynamics and heat transfer when the cylinder is rotating. An optimum value of the distance between the jets was obtained at H = 14 w, where the Nu value was highest for the rotating cylinder case. A modal analysis of the heat transfer dynamics was performed with the POD technique. As diverse applications of energy system technologies with impinging jets are available, considering the rotations of the cooled surface under the combined effects of using magnetic field and nanoparticle loading in heat transfer fluid is a novel contribution. The outcomes of the present work will be helpful in the initial design and optimization studies in applications from electronic cooling to convective drying, solar power and many other systems.

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PAN, Y. Y., C. M. ZHANG, Y. H. ZHAO e R. JUN. "A TETRAD DESCRIPTION ON THE DIRAC SPIN-ROTATION EFFECT". International Journal of Modern Physics D 20, n. 10 (settembre 2011): 1979–82. http://dx.doi.org/10.1142/s0218271811020044.

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Rotation and Dirac spin coupling is described by the tetrad field for a rotating system, where the rotation-spin effect is replaced by an axial torsion-spin. After constructing a rotating tetrad field, we derive the torsion quantities, by which we deal with the torsion-spin coupling.

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Dehghani, M. H., e A. Khodam-Mohammadi. "Hairy rotating black string in the EinsteinMaxwellHiggs system". Canadian Journal of Physics 83, n. 3 (1 marzo 2005): 229–42. http://dx.doi.org/10.1139/p04-083.

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We show numerically that the Abelian Higgs-field equations in the background of a four-dimensional rotating charged black string have vortex solutions. These solutions, which have axial symmetry, establish that the rotating black string can support the Abelian Higgs field as hair. We find an electric field coupled to the Higgs scalar field in the case of a rotating black string. This electric field is due to an electric charge-per-unit-length, which increases as the rotation parameter increases. We also find that the vortex thickness decreases as the rotation parameter increases. Finally, we consider the self-gravity of the Abelian Higgs field and show that the effect of the vortex is to induce a deficit angle in the metric under consideration, which decreases as the rotation parameter increases. PACS Nos.: 04.70.s, 04.40.b, 11.27.+d

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Komarov, Kirill A., Nikita P. Kryuchkov e Stanislav O. Yurchenko. "Tunable interactions between particles in conically rotating electric fields". Soft Matter 14, n. 47 (2018): 9657–74. http://dx.doi.org/10.1039/c8sm01538d.

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Tunable interactions between colloidal particles in external conically rotating electric fields are calculated, while the (vertical) axis of the field rotation is normal to the (horizontal) particle motion plane.

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Prat, V., S. Mathis, B. Buysschaert, J. Van Beeck, D. M. Bowman, C. Aerts e C. Neiner. "Period spacings of gravity modes in rapidly rotating magnetic stars". Astronomy & Astrophysics 627 (luglio 2019): A64. http://dx.doi.org/10.1051/0004-6361/201935462.

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Context. Stellar magnetic fields are often invoked to explain the missing transport of angular momentum observed in models of stellar interiors. However, the properties of an internal magnetic field and the consequences of its presence on stellar evolution are largely unknown. Aims. We study the effect of an axisymmetric internal magnetic field on the frequency of gravity modes in rapidly rotating stars to check whether gravity modes can be used to detect and probe such a field. Methods. Rotation is taken into account using the traditional approximation of rotation and the effect of the magnetic field is computed using a perturbative approach. As a proof of concept, we compute frequency shifts due to a mixed (i.e. with both poloidal and toroidal components) fossil magnetic field for a representative model of a known magnetic, rapidly rotating, slowly pulsating B-type star: HD 43317. Results. We find that frequency shifts induced by the magnetic field scale with the square of its amplitude. A magnetic field with a near-core strength of the order of 150 kG (which is consistent with the observed surface field strength of the order of 1 kG) leads to signatures that are detectable in period spacings for high-radial-order gravity modes. Conclusions. The predicted frequency shifts can be used to constrain internal magnetic fields and offer the potential for a significant step forward in our interpretation of the observed structure of gravity-mode period spacing patterns in rapidly rotating stars.

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Karak, Bidya Binay, Aparna Tomar e Vindya Vashishth. "Stellar dynamos with solar and antisolar differential rotations: Implications to magnetic cycles of slowly rotating stars". Monthly Notices of the Royal Astronomical Society 491, n. 3 (18 novembre 2019): 3155–64. http://dx.doi.org/10.1093/mnras/stz3220.

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ABSTRACT Simulations of magnetohydrodynamics convection in slowly rotating stars predict antisolar differential rotation (DR) in which the equator rotates slower than poles. This antisolar DR in the usual αΩ dynamo model does not produce polarity reversal. Thus, the features of large-scale magnetic fields in slowly rotating stars are expected to be different than stars having solar-like DR. In this study, we perform mean-field kinematic dynamo modelling of different stars at different rotation periods. We consider antisolar DR for the stars having rotation period larger than 30 d and solar-like DR otherwise. We show that with particular α profiles, the dynamo model produces magnetic cycles with polarity reversals even with the antisolar DR provided, the DR is quenched when the toroidal field grows considerably high and there is a sufficiently strong α for the generation of toroidal field. Due to the antisolar DR, the model produces an abrupt increase of magnetic field exactly when the DR profile is changed from solar-like to antisolar. This enhancement of magnetic field is in good agreement with the stellar observational data as well as some global convection simulations. In the solar-like DR branch, with the decreasing rotation period, we find the magnetic field strength increases while the cycle period shortens. Both of these trends are in general agreement with observations. Our study provides additional support for the possible existence of antisolar DR in slowly rotating stars and the presence of unusually enhanced magnetic fields and possibly cycles that are prone to production of superflare.

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Dolginov, A. Z. "Magnetic Field of Rotating Bodies". Symposium - International Astronomical Union 140 (1990): 27–28. http://dx.doi.org/10.1017/s0074180900189442.

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Difficulties of the dynamo and alternative theories of the magnetic field generation are briefly discussed. The correlation between η = lg μ/μo and ζ = lg J/Jo for rotating celestial bodies is considered. μ is the magnetic and J the angular momentum of the body. Existing theories do not explain such a correlation, and it may be an evidence for some new fundamental interaction.

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Kramer, D., e U. Hähner. "A rotating pure radiation field". Classical and Quantum Gravity 12, n. 9 (1 settembre 1995): 2287–96. http://dx.doi.org/10.1088/0264-9381/12/9/015.

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Xiao-Xia Guo, Xiao-Xia Guo, Rui-Qi Zhang Xiao-Xia Guo, Shu-Hao Liu Rui-Qi Zhang, Chen Wan Shu-Hao Liu, Zhen-Yu Wang Chen Wan e Rong-Rong Han Zhen-Yu Wang. "Visualization of Rotating Machinery Noise Based on Near Field Acoustic Holography". 電腦學刊 33, n. 4 (agosto 2022): 215–23. http://dx.doi.org/10.53106/199115992022083304018.

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<p>In order to solve the problem of fast identification of the noise source of rotating machinery, the time-space complex envelope model of monopole sound source is studied, and a modulation method of the complex envelope is proposed. A method combining near-field acoustic holography technology and complex envelope information is proposed to reconstruct the sound field and realize the identification of rotating machinery noise sources. Using the overall fluctuation of the signal to identify the noise source of the rotating machinery greatly reduces the amount of calculation, and speeds up the positioning speed while ensuring the positioning accuracy. According to the sound field radiation characteristics of rotating machinery noise, different measurement distances, different sampling points numbers and different reconstruction distances are selected to reconstruct the sound field. The simulation data analysis results show that the near-field acoustic holography technology can still obtain high sound field reconstruction accuracy under the condition of large reconstruction distance, and does not require high sampling points numbers. Using the envelope information extracted by envelope modulation technology to reconstruct the sound field can accurately identify the number and geometric distribution of sound sources. This technology not only speeds up data processing, but also ensures the accuracy of sound field reconstruction.</p> <p> </p>

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Li, Xiao-Peng, Gao-Pan Kong, Xing Zhang e Guo-Wei He. "Pumping of water through carbon nanotubes by rotating electric field and rotating magnetic field". Applied Physics Letters 103, n. 14 (30 settembre 2013): 143117. http://dx.doi.org/10.1063/1.4824441.

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Vashishth, Vindya, Bidya Binay Karak e Leonid Kitchatinov. "Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: rotation rate dependence". Monthly Notices of the Royal Astronomical Society 522, n. 2 (21 aprile 2023): 2601–10. http://dx.doi.org/10.1093/mnras/stad1105.

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ABSTRACT Like the solar cycle, stellar activity cycles are also irregular. Observations reveal that rapidly rotating (young) Sun-like stars exhibit a high level of activity with no Maunder-like grand minima and rarely display smooth regular activity cycles. On the other hand, slowly rotating old stars like the Sun have low activity levels and smooth cycles with occasional grand minima. We, for the first time, try to model these observational trends using flux transport dynamo models. Following previous works, we build kinematic dynamo models of one solar mass star with different rotation rates. Differential rotation and meridional circulation are specified with a mean-field hydrodynamic model. We include stochastic fluctuations in the Babcock–Leighton source of the poloidal field to capture the inherent fluctuations in the stellar convection. Based on extensive simulations, we find that rapidly rotating stars produce highly irregular cycles with strong magnetic fields and rarely produce Maunder-like grand minima, whereas the slowly rotating stars (with a rotation period of 10 d and longer) produce smooth cycles of weaker strength, long-term modulation in the amplitude, and occasional extended grand minima. The average duration and the frequency of grand minima increase with decreasing rotation rate. These results can be understood as the tendency of less supercritical dynamo in slower rotating stars to be more prone to produce extended grand minima.

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Chau, Yeung Yeung, Ruo-Yang Zhang e Weijia Wen. "Reverse rotation of soft ferromagnetic ball in rotating magnetic field". Journal of Magnetism and Magnetic Materials 476 (aprile 2019): 376–81. http://dx.doi.org/10.1016/j.jmmm.2018.12.073.

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Kolsi, Lioua, Fatih Selimefendigil, Samia Larguech, Kaouther Ghachem, Hind Albalawi, Badr M. Alshammari e Taher Labidi. "Convective Heat Transfer and Entropy Generation for Nano-Jet Impingement Cooling of a Moving Hot Surface under the Effects of Multiple Rotating Cylinders and Magnetic Field". Mathematics 11, n. 8 (17 aprile 2023): 1891. http://dx.doi.org/10.3390/math11081891.

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In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher.

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Gu, Guo-Qing, e En-Bo Wei. "Torque exerting on suspended particles in rotating electric field". International Journal of Modern Physics B 35, n. 13 (20 maggio 2021): 2150164. http://dx.doi.org/10.1142/s0217979221501642.

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In this paper, rotation properties of suspended particles under an external rotating electric field (EREF) are investigated. Based on the re-distribution of surface-induced charges on moving particles, the torque exerting on particles by EREF is derived analytically. Furthermore, for the sol suspended in Newtonian fluid, the angular velocity of the rotating particle is formulated by the EREF and the dielectric constants of the particle and matrix. The result shows that the angular velocity of particles depends on the angular velocity of EREF, and is proportional to the square of EREF strength. The maximum angular velocity of rotating particles is reached if the angular velocity of EREF is equal to the reciprocal of the relaxation time of the induced charge.

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Sharma, Praveen Kumar, Shraddha Argal, Anita Tiwari e Ram Prasad Prajapati. "Jeans Instability of Rotating Viscoelastic Fluid in the Presence of Magnetic Field". Zeitschrift für Naturforschung A 70, n. 1 (1 gennaio 2015): 39–45. http://dx.doi.org/10.1515/zna-2014-0229.

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AbstractThe Jeans instability of rotating viscoelastic fluid in the presence of uniform magnetic field is investigated using the generalised hydrodynamic (GH) model. A general dispersion relation is derived with the help of linearised perturbation equations using the normal mode analysis, which is further discussed for axis of rotation parallel and perpendicular to the direction of the magnetic field in both the weakly coupled (hydrodynamic) and strongly coupled (kinetic) limits. The onset criterion of Jeans instability for magnetised rotating viscoelastic fluid is obtained, which remains unaffected by the presence of rotation and magnetic field but depends upon viscoelastic effects. The graphical illustrations are depicted to see the influence of rotation, Mach number, shear and viscous effects, and sound speed on the growth rate of Jeans instability. It is found that all these parameters have stabilising influence on the growth rate of Jeans instability; hence, they are capable of collapsing to a self-gravitating, rotating, magnetised viscoelastic medium.

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Bhatia, P. K., e R. P. Mathur. "Stability Of Rotating Gravitating Streams". Zeitschrift für Naturforschung A 60, n. 7 (1 luglio 2005): 484–88. http://dx.doi.org/10.1515/zna-2005-0703.

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This paper treats the stability of two superposed gravitating streams rotating about the axis transverse to the horizontal magnetic field. The critical wave number for instability is found to be affected by rotation for propagation perpendicular to the axis about which the system rotates. The critical wave number for instability is not affected by rotation when waves propagate along the axis of rotation. The critical wave number is affected by both the magnetic field and the streaming velocity in both cases. Both the magnetic field and the rotation are stabilizing, while the streaming velocity is destabilizing.

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Tyatyushkin, Alexander. "Influence of Rotation on the Magnetization of Dilute Suspensions of Magnetic Particles". Solid State Phenomena 233-234 (luglio 2015): 302–5. http://dx.doi.org/10.4028/www.scientific.net/ssp.233-234.302.

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The influence of rotation on the magnetization of a suspension of spherical magnetic particles in a uniform magnetic field is investigated theoretically with taking into account the inertial effects. A rotation of a single spherical non-Brownian particle with an embedded magnetic moment under action of a rotational flow of the ambient liquid in an applied uniform magnetic field is considered. The system of equations is obtained that determines the rotation of the particle and the instant orientation of its magnetic dipole moment with taking into account both the inertia of the particles and that of the dispersion liquid of the suspension. The magnetization vector of a suspension of non-Brownian spherical magnetic particles is found for the suspension rotating in a uniform constant magnetic field and for that rotating in a sufficiently weak uniform alternating magnetic field. The system of equations is obtained for the function of distribution over the orientations of the magnetic dipole moments for a suspension of Brownian spherical magnetic particles rotating in a uniform magnetic field. The solution to this system of equations is obtained for a suspension rotating in a sufficiently weak alternating magnetic field. With the use of this solution, the magnetization vector of the suspension is found.

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Keszthelyi, Z., G. Meynet, C. Georgy, G. A. Wade, V. Petit e A. David-Uraz. "The effects of surface fossil magnetic fields on massive star evolution: I. Magnetic field evolution, mass-loss quenching, and magnetic braking". Monthly Notices of the Royal Astronomical Society 485, n. 4 (20 marzo 2019): 5843–60. http://dx.doi.org/10.1093/mnras/stz772.

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Abstract Surface magnetic fields have a strong impact on stellar mass loss and rotation and, as a consequence, on the evolution of massive stars. In this work, we study the influence of an evolving dipolar surface fossil magnetic field with an initial field strength of 4 kG on the characteristics of 15 M⊙ solar metallicity models using the Geneva stellar evolution code. Non-rotating and rotating models considering two different scenarios for internal angular momentum transport are computed, including magnetic field evolution, mass-loss quenching, and magnetic braking. Magnetic field evolution results in weakening the initially strong magnetic field; however, in our models, an observable magnetic field is still maintained as the star evolves towards the red supergiant phase. At the given initial mass of the models, mass-loss quenching is modest. Magnetic braking greatly enhances chemical element mixing if radial differential rotation is allowed for; on the other hand, the inclusion of surface magnetic fields yields a lower surface enrichment in the case of near solid-body rotation. Models including surface magnetic fields show notably different trends on the Hunter diagram (plotting nitrogen abundance versus vsin i) compared to those that do not. The magnetic models agree qualitatively with the anomalous ‘Group 2 stars’, showing slow surface rotation and high surface nitrogen enhancement on the main sequence.

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Sakellariou, Dimitris, Carlos A. Meriles, Rachel W. Martin e Alexander Pines. "NMR in rotating magnetic fields: magic-angle field spinning". Magnetic Resonance Imaging 23, n. 2 (febbraio 2005): 295–99. http://dx.doi.org/10.1016/j.mri.2004.11.067.

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Núñez, Manuel. "An Analytic Study of the Reversal of Hartmann Flows by Rotating Magnetic Fields". International Journal of Mathematics and Mathematical Sciences 2012 (2012): 1–15. http://dx.doi.org/10.1155/2012/641738.

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The effects of a background uniform rotating magnetic field acting in a conducting fluid with a parallel flow are studied analytically. The stationary version with a transversal magnetic field is well known as generating Hartmann boundary layers. The Lorentz force includes now one term depending on the rotation speed and the distance to the boundary wall. As one intuitively expects, the rotation of magnetic field lines pushes backwards or forwards the flow. One consequence is that near the wall the flow will eventually reverse its direction, provided the rate of rotation and/or the magnetic field are large enough. The configuration could also describe a fixed magnetic field and a rotating flow.

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30

Shvarts, K. G. "Advective Flow of a Rotating Fluid Layer in a Vibrational Field". Nelineinaya Dinamika 15, n. 3 (2019): 261–70. http://dx.doi.org/10.20537/nd190305.

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31

Matsuki, Yoshio, e Petro Bidyuk. "Simulation of a rotating strong gravity that reverses time". System research and information technologies, n. 3 (18 novembre 2021): 7–16. http://dx.doi.org/10.20535/srit.2308-8893.2021.3.01.

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In this research we simulated how time can be reversed with a rotating strong gravity. At first, we assumed that the time and the space can be distorted with the presence of a strong gravity, and then we calculated the angular momentum density of the rotating gravitational field. For this simulation we used Einstein’s field equation with spherical polar coordinates and the Euler’s transformation matrix to simulate the rotation. We also assumed that the stress-energy tensor that is placed at the end of the strong gravitational field reflects the intensities of the angular momentum, which is the normal (perpendicular) vector to the rotating axis. The result of the simulation shows that the angular momentum of the rotating strong gravity changes its directions from plus (the future) to minus (the past) and from minus (the past) to plus (the future), depending on the frequency of the rotation.

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32

Li, Lei, Chunhua Zhu, Sufen Guo, Helei Liu e Guoliang Lü. "The Effects of Rotation, Metallicity, and Magnetic Field on the Islands of Failed Supernovae". Astrophysical Journal 952, n. 1 (1 luglio 2023): 79. http://dx.doi.org/10.3847/1538-4357/acd9ca.

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Abstract Failed supernovae (FSN) are a possible channel for the formation of heavy stellar-mass black holes (M BH > ∼30 M ⊙). However, the effects of metallicity, rotation, and magnetic field on the islands of explodabilty of massive stars are not clear. Here, we simulate the stellar structure and evolution in the mass range between 6 and 55 M ⊙ with different initial rotational velocities, metallicities, and magnetic fields from zero-age main sequence (ZAMS) to pre-collapse. We find that the rapid rotating stars can remain lower 12C mass fraction at the time of C ignition, which allows the transition, from convective carbon burning to radiative burning, to occur at lower M ZAMS than those from stars without rotation. However, the rapid rotation is unfavorable for FSN occurring but is conducive to long gamma-ray bursts (lGRBs) because it results in the specific angular momentum in the CO core being greater than the last stable orbit at core collapse. The increasing metallicity does not affect FSN islands, but high metallicity inhibits rotational mixing and is unfavorable for producing lGRBs. A magnetic field can constrain the mass-loss rate even for rapid rotating stars, resulting in higher mass at pre-collapse. The magnetic braking triggered by the magnetic field can reduce the rotation velocity for high-metallicity models, which decreases the specific angular momentum in the CO core and is favorable for FSN occurring. We suggest that the heavy-mass black holes detected by LIGO may originate from rapidly rotating massive stars with strong magnetic fields, rather than those with very low metallicity.

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33

Prat, V., S. Mathis, C. Neiner, J. Van Beeck, D. M. Bowman e C. Aerts. "Period spacings of gravity modes in rapidly rotating magnetic stars". Astronomy & Astrophysics 636 (aprile 2020): A100. http://dx.doi.org/10.1051/0004-6361/201937398.

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Abstract (sommario):

Context. Stellar internal magnetic fields have recently been shown to leave a detectable signature on period spacing patterns of gravity modes. Aims. We aim to investigate the effect of the obliquity of a mixed (poloidal and toroidal) dipolar internal fossil magnetic field with respect to the rotation axis on the frequency of gravity modes in rapidly rotating stars. Methods. We used the traditional approximation of rotation to compute non-magnetic modes, and a perturbative treatment of the magnetic field to compute the corresponding frequency shifts. We applied the new formalism to HD 43317, a magnetic, rapidly rotating, slowly pulsating B-type star, whose field has an obliquity angle of about 80°. Results. We find that frequency shifts induced by the magnetic field on high-radial-order gravity modes are larger with increasing obliquity angle, when the magnetic axis is closer to the equatorial region, where these modes are trapped. The maximum value is reached for an obliquity angle of 90°. This trend is observed for all mode geometries. Conclusions. Our results predict that the signature of an internal oblique dipolar magnetic field is detectable using asteroseismology of gravity modes.

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34

Soong, C. Y. "Thermal Buoyancy Effects in Rotating Non-Isothermal Flows". International Journal of Rotating Machinery 7, n. 6 (2001): 435–46. http://dx.doi.org/10.1155/s1023621x01000380.

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The present paper is concerned with the non-isothermal flow mechanisms in rotating systems with emphasis on the rotation-induced thermal buoyancy effects stemming from the coexistence of rotational body forces and the nonuniformity of the fluid temperature field. Non-isothermal flow in rotating ducts of radial and parallel modes and rotating cylindrical configurations, including rotating cylinders and disk systems, are considered. Previous investigations closely related to the rotational buoyancy are surveyed. The mechanisms of the rotation-induced buoyancy are manifested by the author's recent theoretical results and scaling analyses pertaining to the rotation-induced buoyancy in rotating ducts and two-disk systems. Finally, the open issues for future researches in this area are proposed.

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35

Ardeljan, N. V., G. S. Bisnovatyi-Kogan e S. G. Moiseenko. "Magnetorotational Mechanism: Supernova Explosions and Ejections". Symposium - International Astronomical Union 214 (2003): 117–20. http://dx.doi.org/10.1017/s0074180900194252.

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Abstract (sommario):

We made simulations of the collapse of the rotating protostellar cloud. Differential rotation leads to the amplification of the toroidal component of the magnetic field and subsequent ejection of the matter due to the magnetorotational mechanism.Our results show that at different initial configurations of the magnetic field formation of qualitatively different types of explosion takes place. Magnetic field of the dipole type produces a jet-like explosion. Quadrupole-like magnetic field produces supernova explosion whith ejection presumably near equatorial plane. Quantitative estimations of the ejected mass and energy are given.We have done simulation of the collapse of the white dwarf and formation of a differentially rotating neutron star. After the collapse stage the rotating neutron star was formed. The rotation of the neutron star is strongly differential. The presence of the magnetic field (even the weak one) could produce magnetorotational supernova explosion.For the simulations we have used 2D numerical scheme, based on the specially developed numerical method (conservative, implicit, triangular grid, Lagrangian, grid reconstruction).

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36

YU, K. W., G. Q. GU, J. P. HUANG e J. J. XIAO. "DYNAMIC ELECTRORHEOLOGICAL EFFECTS OF ROTATING PARTICLES: A BRIEF REVIEW". International Journal of Modern Physics B 19, n. 07n09 (10 aprile 2005): 1163–69. http://dx.doi.org/10.1142/s0217979205030013.

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Abstract (sommario):

Particle rotation leads to a steady-state which is different from the equilibrium state in the absence of rotational motion. The change of the polarization of the particle due to the rotational motion is called the dynamic electrorheological effect (DER). There are three cases to be considered: rotating particles in a dc field, particle rotation due to a rotating field and spontaneous rotation of particle in dc field (Quincke rotation). In the DER of rotating particles, the particle rotational motion generally reduces the interparticle force between the particles. The effect becomes pronounced when the frequency is on the order of the relaxation rate of the surface charges. In the electrorotation of particles, the mutual interaction between approaching particles will change the electrorotation spectrum significantly. The electrorotation spectrum depends strongly on the medium conductivity as well as the conductivity contrast between the particle and the medium. In the collective behaviors of Quincke rotors, the mutual interactions between the individual rotors lead to the assembly of chain-like structures which make an angle with the applied field. This has an implication of a new class of material.

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37

Zhang, Kechen, Martin I. Sereno e Margaret E. Sereno. "Emergence of Position-Independent Detectors of Sense of Rotation and Dilation with Hebbian Learning: An Analysis". Neural Computation 5, n. 4 (luglio 1993): 597–612. http://dx.doi.org/10.1162/neco.1993.5.4.597.

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Abstract (sommario):

We previously demonstrated that it is possible to learn position-independent responses to rotation and dilation by filtering rotations and dilations with different centers through an input layer with MT-like speed and direction tuning curves and connecting them to an MST-like layer with simple Hebbian synapses (Sereno and Sereno 1991). By analyzing an idealized version of the network with broader, sinusoidal direction-tuning and linear speed-tuning, we show analytically that a Hebb rule trained with arbitrary rotation, dilation/contraction, and translation velocity fields yields units with weight fields that are a rotation plus a dilation or contraction field, and whose responses to a rotating or dilating/contracting disk are exactly position independent. Differences between the performance of this idealized model and our original model (and real MST neurons) are discussed.

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38

Umehara, Noritsugu, Koji Kato e Haruhisa Nakano. "Rotation of Nonmagnetic Body in Magnetic Fluid under Rotating Magnetic Field." Transactions of the Japan Society of Mechanical Engineers Series B 60, n. 578 (1994): 3327–35. http://dx.doi.org/10.1299/kikaib.60.3327.

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39

Baba, Shoko, e Satoshi Tanaka. "Particle Rotation in Colloidal Processing under a Strong Rotating Magnetic Field". Langmuir 34, n. 22 (3 maggio 2018): 6462–69. http://dx.doi.org/10.1021/acs.langmuir.7b04344.

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40

Petrov, Yuri, Xiaokang Yang e Tian-Sen Huang. "Magnetic field structure evolution in rotating magnetic field plasmas". Physics of Plasmas 15, n. 7 (luglio 2008): 072509. http://dx.doi.org/10.1063/1.2952293.

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41

Nakane, H., S. Omori e I. Yokoshima. "Standard RF magnetic field from a rotating field generator". IEEE Transactions on Instrumentation and Measurement IM-35, n. 3 (settembre 1986): 358–60. http://dx.doi.org/10.1109/tim.1986.6499225.

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42

Tajmar, M., e C. J. de Matos. "Gravitomagnetic field of a rotating superconductor and of a rotating superfluid". Physica C: Superconductivity 385, n. 4 (aprile 2003): 551–54. http://dx.doi.org/10.1016/s0921-4534(02)02305-5.

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43

KOBAYASHI, Akira, e Shinji OOYAMA. "Fundamental Study on Optical Rotating Field". Transactions of the Society of Instrument and Control Engineers 21, n. 11 (1985): 1202–9. http://dx.doi.org/10.9746/sicetr1965.21.1202.

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44

Cacciola, Matteo, Diego Pellicano, Giuseppe Megali, Salvatore Calcagno e Francesco Carlo Morabito. "ROTATING ELECTROMAGNETIC FIELD FOR NDT INSPECTIONS". Progress In Electromagnetics Research B 22 (2010): 305–20. http://dx.doi.org/10.2528/pierb10052409.

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45

Maksimenko, V. G. "Rotating Electrode in Electric-Field Sensor". Journal of Communications Technology and Electronics 66, n. 5 (maggio 2021): 561–66. http://dx.doi.org/10.1134/s1064226921040070.

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46

Kraftmakher, Yaakov. "Two experiments with rotating magnetic field". European Journal of Physics 22, n. 5 (20 luglio 2001): 477–82. http://dx.doi.org/10.1088/0143-0807/22/5/302.

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47

Georgiou, A. "The electromagnetic field in rotating coordinates". Proceedings of the IEEE 76, n. 8 (1988): 1051–52. http://dx.doi.org/10.1109/5.5974.

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48

TURAKULOV, Z. YA. "RELATIVISTIC ROTATING DISK: THE EXTERNAL FIELD". International Journal of Modern Physics A 04, n. 14 (20 agosto 1989): 3653–63. http://dx.doi.org/10.1142/s0217751x8900145x.

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Abstract (sommario):

Three-parametric family of models of the space-time containing an infinitesimally thin rotating disk is constructed. The manifolds are piecewise-smooth and consist of two smooth regions which are the Kerr space pieces. The curvature has the singularity on the common boundary of the smooth regions in the form of one-dimensonal δ-function and the Einstein tensor consists of its singular terms only. The boundary forms the source of the gravitational field which is an infinitesimally thin disk in form. It is shown that each geodesic tangent to the disk is wholly lying on it. The shape of the Einstein tensor indicates the absence of the pressure and motion of the source matter in the direction normal to the disk.

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49

ROMA�KEVI�IUS, Olegas. "Technological Inductors of Rotating Magnetic Field". PRZEGLĄD ELEKTROTECHNICZNY 1, n. 2 (5 febbraio 2016): 84–86. http://dx.doi.org/10.15199/48.2016.02.24.

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50

Bologna, M., B. Tellini e F. Giraldi. "Plasma in a Rotating Magnetic Field". IEEE Transactions on Plasma Science 36, n. 1 (febbraio 2008): 140–45. http://dx.doi.org/10.1109/tps.2007.913930.

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