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Articles de revues sur le sujet « Time-harmonic field »

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Auteur : Grafiati
Publié le 10 mars 2023

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1

Faul, Fabian T., Jonas Kornprobst, Torsten Fritzel, Hans-Jürgen Steiner, Rüdiger Strauß, Alexander Weiß, Robert Geise et Thomas F. Eibert. « Near-field measurement of continuously modulated fields employing the time-harmonic near- to far-field transformation ». Advances in Radio Science 17 (19 septembre 2019) : 83–89. http://dx.doi.org/10.5194/ars-17-83-2019.

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Abstract. Near-field far-field transformations (NFFFTs) are commonly performed for time-harmonic fields. Considering arbitrary in-situ measurement scenarios with given transmission signals, time-varying aspects of modulated signals have to be taken into consideration. We investigate and characterize two methods for the measurement of modulated fields, which work with a time-domain representation of the radiated fields and, at the same time, allow to employ the standard time-harmonic NFFFT. One method is based on the fact that the modulation signal can be assumed to be constant in a short enough measurement interval under the condition that the modulation and carrier frequencies are several decades apart. The second method performs long-time measurements in order to obtain the complete frequency spectrum in every single measurement. Both methods are verified by the NFFFT of synthetic field data.
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2

Banchs, R. E., et F. X. Bostick. « Time-harmonic field analysis of electric logging systems ». IEEE Transactions on Geoscience and Remote Sensing 40, no 6 (juin 2002) : 1427–30. http://dx.doi.org/10.1109/tgrs.2002.800752.

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3

Gralak, Boris, et Daniel Maystre. « Negative index materials and time-harmonic electromagnetic field ». Comptes Rendus Physique 13, no 8 (octobre 2012) : 786–99. http://dx.doi.org/10.1016/j.crhy.2012.04.003.

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4

Qian, S. W., Y. T. Hu et J. S. Wang. « Time-dependent harmonic oscillators in an electromagnetic field ». Journal of Physics A : Mathematical and General 20, no 10 (11 juillet 1987) : 2833–41. http://dx.doi.org/10.1088/0305-4470/20/10/027.

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5

Yüce, Cem. « Exact solution of the time-dependent harmonic plus an inverse harmonic potential with a time-dependent electromagnetic field ». Annals of Physics 308, no 2 (décembre 2003) : 599–604. http://dx.doi.org/10.1016/s0003-4916(03)00175-1.

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6

Schaller, Richard D., Justin C. Johnson et Richard J. Saykally. « Time-Resolved Second Harmonic Generation Near-Field Scanning Optical Microscopy ». ChemPhysChem 4, no 11 (6 novembre 2003) : 1243–47. http://dx.doi.org/10.1002/cphc.200300907.

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7

Liu, Wensen, et Jisuo Wang. « Time evolution of a time-dependent harmonic oscillator in a static magnetic field ». Journal of Physics A : Mathematical and Theoretical 40, no 5 (17 janvier 2007) : 1057–63. http://dx.doi.org/10.1088/1751-8113/40/5/013.

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8

Gold, Alysson, et Sami Tantawi. « A Classical Field Theory Formulation for the Numerical Solution of Time Harmonic Electromagnetic Fields ». IEEE Journal on Multiscale and Multiphysics Computational Techniques 4 (2019) : 245–59. http://dx.doi.org/10.1109/jmmct.2019.2950555.

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9

QIAO, H. X., Y. C. ZOU et Z. J. ZHANG. « HIGH-ORDER HARMONIC GENERATION OF HYDROGEN IN INTENSE LASER FIELD AND STRONG MAGNETIC FIELD ». International Journal of Modern Physics C 15, no 04 (mai 2004) : 493–506. http://dx.doi.org/10.1142/s0129183104005899.

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An effective one-dimensional model approach combining time-dependent pseudospectral method and Taylor expansion [Haoxue Qiao et al., Phys. Rev. A65, 063403 (2002)] is generalized to study a real hydrogen atom in an intense laser field. High-order harmonic generations are calculated in several cases of different laser field parameters. The ionization probability is also calculated. The influence of the strong magnetic field on harmonic generations is investigated. It is found that the plateau of high harmonics can be extended by the magnetic field and the cutoff order increases with the increase of the field intensity.
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10

PINTO, TIAGO, et JEAN-PIERRE COYETTE. « CONJUGATED INFINITE ELEMENTS FOR TWO-DIMENSIONAL TIME-HARMONIC ELASTODYNAMICS ». Journal of Computational Acoustics 08, no 03 (septembre 2000) : 473–93. http://dx.doi.org/10.1142/s0218396x00000327.

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Wave propagation problems in unbounded domains require the handling of appropriate radiation conditions (Sommerfeld). Various absorbing boundary conditions are available for that purpose. In a discrete finite element context, local and global Dirichlet-to-Neumann (DtN) and infinite element methods have shown their efficiency for the scalar wave equation. The paper concentrates on the extension of an infinite element method to the elastodynamic vector wave equation. The extension is developed in the frequency domain for 2-D problems. The paper focuses on the development of a conjugated formulation using the Helmholtz decomposition theorem of smooth vector fields. The accuracy of the developed formulation is assessed through the study of benchmarks. The computed results are shown to be in good agreement with the analytical solution for a multi-pole field along a circular cavity and with the results produced by other numerical methods.
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11

Jansari, Chintan, Javier Videla, Sundararajan Natarajan, Stéphane P. A. Bordas et Elena Atroshchenko. « Adaptive enriched geometry independent field approximation for 2D time-harmonic acoustics ». Computers & ; Structures 263 (avril 2022) : 106728. http://dx.doi.org/10.1016/j.compstruc.2021.106728.

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12

Marticorena Garcia, Stephan Rodrigo, Markus Grossmann, Sophia Theresa Lang, Manh Nguyen Trong, Michael Schultz, Jing Guo, Bernd Hamm, Jürgen Braun, Ingolf Sack et Heiko Tzschätzsch. « Full-Field-of-View Time-Harmonic Elastography of the Native Kidney ». Ultrasound in Medicine & ; Biology 44, no 5 (mai 2018) : 949–54. http://dx.doi.org/10.1016/j.ultrasmedbio.2018.01.007.

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13

Gąsiorski, A. K. « Non-symmetrical shaped conductors located in a time-harmonic TM field ». Archiv für Elektrotechnik 69, no 1 (janvier 1986) : 1–9. http://dx.doi.org/10.1007/bf01573975.

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14

Ateş, Ülkü Dinlemez. « Properties of the far field operator for time harmonic acoustic waves ». Applied Mathematics and Computation 174, no 2 (mars 2006) : 1206–15. http://dx.doi.org/10.1016/j.amc.2005.06.008.

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15

Fernandez-Corbaton, Ivan. « A Conformally Invariant Derivation of Average Electromagnetic Helicity ». Symmetry 11, no 11 (19 novembre 2019) : 1427. http://dx.doi.org/10.3390/sym11111427.

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The average helicity of a given electromagnetic field measures the difference between the number of left- and right-handed photons contained in the field. Here, the average helicity is derived using the conformally invariant inner product for Maxwell fields. Several equivalent integral expressions in momentum space, in ( r , t ) space, and in the time-harmonic ( r , ω ) space are obtained, featuring Riemann–Silberstein-like fields and potentials. The time-harmonic expressions can be directly evaluated using the outputs of common numerical solvers of Maxwell equations. The results are shown to be equivalent to the well-known volume integral for the average helicity, featuring the electric and magnetic fields and potentials.
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16

Wang, Yunhui, Dandan Song, Qiang Zuo, Hong Wu et Zhihong Yang. « High-order harmonic generation with a single-color mid-infrared laser field by frequency-chirping ». International Journal of Modern Physics B 33, no 13 (20 mai 2019) : 1950122. http://dx.doi.org/10.1142/s0217979219501224.

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By numerically solving the time-dependent Schrödinger equation for helium atoms in a single mid-infrared laser field, we explore the frequency-chirping effect of laser field on high-order harmonic and isolated attosecond pulse generation. One or two ultrabroad supercontinuum harmonic plateaus can be controlled through modulating the laser field frequency by a small time-dependent signal. Under the best chirping condition, an ultrashort 2.2 as pulse can be obtained by Fourier transformation with the bandwidth of 782 eV. Furthermore, we explain the harmonic generation physical mechanisms by classical ionizing and returning energy maps and time–frequency analyzes.
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17

Tinkelman, Igor, et Timor Melamed. « Local spectrum analysis of field propagation in an anisotropic medium Part I Time-harmonic fields ». Journal of the Optical Society of America A 22, no 6 (1 juin 2005) : 1200. http://dx.doi.org/10.1364/josaa.22.001200.

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18

Cai, Li Ming, Hui Qi et Xiang Nan Pan. « The Scattering of Circular Cylindrical Cavity with Time-Harmonic SH Waves in Infinite Strip Region ». Applied Mechanics and Materials 580-583 (juillet 2014) : 3083–88. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.3083.

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The scattering of time harmonic SH waves by arbitrary positions of circular cylindrical cavity is studied in continuous, homogeneous, isotropic, elastic strip region. In this paper, the completely analytical expression of total wave field is explicitly presented and the dynamic stress distribution is symbolically visualized in the strip region. The total wave field is divided into four sub wave fields, incident wave field and scattering wave field by the upper bound, the lower bound and the cylindrical bound, on big arc supposition. Specific wave functions are employed for each wave field expansion in series, such as circular cylindrical functions, respectively. Corresponding infinite linear algebraic equations are constructed by means of solving coefficients of Fourier series expansion on each sub wave field. Coefficients of cylindrical function expansion of each sub wave field are determined by truncated equations, which are reduced number of coefficients on pre-given computational accuracy. Numerical results graphically describe the dynamic stress concentration factor around the circumference of the cavity and the normalized dynamic stress along the cross section directly above the cavity.
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19

Zhou, Renlong, Mengxiong Wu, Hui Deng, Qiong Liu, Suxia Xie, Lingxi Wu, Guozheng Nie et Jie Zhan. « High Absorption and Second-Harmonic Generation in Split Ring Resonator Multilayer Nanostructure ». Journal of Nanomaterials 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/150957.

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Second-harmonic generation in split ring resonator multilayer nanostructure is studied with the finite-difference time-domain (FDTD) method. The fundamental frequency wave and the second-harmonic generation at the resonant absorption wavelength are highly localized in the dielectric layer, and the absorption peak is sensitive to dielectric constant of the dielectric layer. Under the excitation of the plasmon resonances mode, the strong local field induces an expected increase of the second-harmonic generation with conversion efficiencies 10−6-10−7. The distributions of fundamental frequency electric field and second-harmonic electric field inside the central dielectric layer region are also shown.
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20

Habibović, Dino, Wilhelm Becker et Dejan B. Milošević. « Symmetries and Selection Rules of the Spectra of Photoelectrons and High-Order Harmonics Generated by Field-Driven Atoms and Molecules ». Symmetry 13, no 9 (25 août 2021) : 1566. http://dx.doi.org/10.3390/sym13091566.

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Using the strong-field approximation we systematically investigate the selection rules for high-order harmonic generation and the symmetry properties of the angle-resolved photoelectron spectra for various atomic and molecular targets exposed to one-component and two-component laser fields. These include bicircular fields and orthogonally polarized two-color fields. The selection rules are derived directly from the dynamical symmetries of the driving field. Alternatively, we demonstrate that they can be obtained using the conservation of the projection of the total angular momentum on the quantization axis. We discuss how the harmonic spectra of atomic targets depend on the type of the ground state or, for molecular targets, on the pertinent molecular orbital. In addition, we briefly discuss some properties of the high-order harmonic spectra generated by a few-cycle laser field. The symmetry properties of the angle-resolved photoelectron momentum distribution are also determined by the dynamical symmetry of the driving field. We consider the first two terms in a Born series expansion of the T matrix, which describe the direct and the rescattered electrons. Dynamical symmetries involving time translation generate rotational symmetries obeyed by both terms. However, those that involve time reversal generate reflection symmetries that are only observed by the direct electrons. Finally, we explain how the symmetry properties, imposed by the dynamical symmetry of the driving field, are altered for molecular targets.
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21

Liu, De Hong, Xiang Jun Wang, Wu Bing Zhu et Dou Ji. « Propagation Characteristic Analysis of Shaft-Rated Electromagnetic Field Produced by Ship of Multiple Propellers in Shallow Ocean ». Applied Mechanics and Materials 475-476 (décembre 2013) : 1428–32. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.1428.

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In order to discuss the propagation characteristic of shaft-rated (SR) electromagnetic (EM) field produced by the ship of multiple propellers in shallow ocean, analytical expressions of EM was derived by several time-harmonic vertical dipoles model based on single time-harmonic vertical dipole method. Firstly, the paper built the physical model of single time-harmonic vertical dipole in triple-layer mediums with uniform speed movement. Then from two factors of phase and frequency, according to vector superposition principle, the EM expressions were solved by n time-harmonic vertical dipoles in fixed position so as to provide theoreticl law for the research of propagation characteristic. Some valuable conclusions were rearched through simulation, including finding the maxmum EM value when frequency was same and phase was zero, and frepuency variation was no-effect to the SR EM field when phase was same. Lastly, the exprement results were anatomotic with theoreticl analysis and demonstrated the effectiveness the expressions.
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22

Sun, Huiyuan, Thushara D. Abhayapala et Prasanga N. Samarasinghe. « Time Domain Spherical Harmonic Processing with Open Spherical Microphones Recording ». Applied Sciences 11, no 3 (25 janvier 2021) : 1074. http://dx.doi.org/10.3390/app11031074.

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Spherical harmonic analysis has been a widely used approach for spatial audio processing in recent years. Among all applications that benefit from spatial processing, spatial Active Noise Control (ANC) remains unique with its requirement for open spherical microphone arrays to record the residual sound field throughout the continuous region. Ideally, a low delay spherical harmonic recording algorithm for open spherical microphone arrays is desired for real-time spatial ANC systems. Currently, frequency domain algorithms for spherical harmonic decomposition of microphone array recordings are applied in a spatial ANC system. However, a Short Time Fourier Transform is required, which introduces undesirable system delay for ANC systems. In this paper, we develop a time domain spherical harmonic decomposition algorithm for the application of spatial audio recording mainly with benefit to ANC with an open spherical microphone array. Microphone signals are processed by a series of pre-designed finite impulse response (FIR) filters to obtain a set of time domain spherical harmonic coefficients. The time domain coefficients contain the continuous spatial information of the residual sound field. We corroborate the time domain algorithm with a numerical simulation of a fourth order system, and show the proposed method to have lower delay than existing approaches.
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23

Vergel, Daniel Gómez, et Eduardo J. S. Villaseñor. « The time-dependent quantum harmonic oscillator revisited : Applications to quantum field theory ». Annals of Physics 324, no 6 (juin 2009) : 1360–85. http://dx.doi.org/10.1016/j.aop.2009.03.003.

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24

Li, Yi, R. Liqiang Feng et Yan Qiao. « Improvement of harmonic spectra from superposition of initial state driven by homogeneous and inhomogeneous combined field ». Canadian Journal of Physics 98, no 2 (février 2020) : 198–209. http://dx.doi.org/10.1139/cjp-2019-0002.

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A larger harmonic cutoff with a higher harmonic yield is a necessary requirement for producing intense ultrashort extreme ultraviolet (XUV) and X-ray sources. In this paper, we present a potential method to improve the harmonic cutoff and harmonic yield from the superposition of initial states in the He atom driven by the low-intensity homogeneous and inhomogeneous combined field. The results can be separated into two parts, that is, (i) the extension of harmonic cutoff via the optimization of three-color homogeneous and inhomogeneous field (covering the carrier envelope phase, delay time, intensity ratio, and inhomogeneous effect); and (ii) the enhancement of harmonic yield via the superposition of ground state and excited state as the initial state. Consequently, a water window harmonic plateau with an intensity enhancement of six orders of magnitude can be obtained. Moreover, the harmonic plateau is contributed by a single harmonic emission peak. Finally, through the Fourier transformation of some selected harmonics on the spectral continuum, a number of sub-50 as water window attosecond pulses with the intensity enhancement of six orders of magnitude can be obtained.
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25

Silaev, A. A., A. A. Romanov et N. V. Vvedenskii. « High Harmonic Generation from Oriented Asymmetric Molecules in the Presence of Static Electric Field ». Journal of Physics : Conference Series 2249, no 1 (1 avril 2022) : 012004. http://dx.doi.org/10.1088/1742-6596/2249/1/012004.

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Abstract We investigate the high harmonic generation during the interaction of the femtosecond laser field with oriented asymmetric diatomic molecules in the presence of an external static electric field. Based on the numerical solution of the time-dependent Schrödinger equation for the model one-electron system, we calculate the high harmonic generation spectrum for a wide range of static-field strengths. The possibilities for visualizing low-frequency (terahertz and mid-infrared) radiation using time-delay measurements of even high harmonics intensities are discussed.
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26

Lan, Wendi, Xinyu Wang, Yue Qiao, Shushan Zhou, Jigen Chen, Jun Wang, Fuming Guo et Yujun Yang. « High-Intensity Harmonic Generation with Energy Tunability Produced by Robust Two-Color Linearly Polarized Laser Fields ». Symmetry 15, no 3 (23 février 2023) : 580. http://dx.doi.org/10.3390/sym15030580.

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By using the numerical solution of the time-dependent Schrödinger equation, we theoretically explored the high-order harmonic generation process under the interaction of high-intensity two-color ultrashort driving laser pulses with atoms. The symmetry of the electric field of the laser pulse will be broken. The producing electric field was controlled at the subcycle level by an IR laser and its second harmonic, which has the unique characteristic that two sequential half-cycles become distinct, rather than merely opposite in sign. Compared with the case of the atom in the fundamental laser pulse, the harmonic efficiency showed an increase of 1∼2 orders of magnitude at specific harmonic order with this combined pulse action. Through the theoretical analysis with the “three-step model”, it was demonstrated that the enhancement of the harmonic intensity is due to the fast ionization of electrons at the ionization moment and the short time from ionization to recombination of ionized electrons. In addition, effects of the peak field amplitude ratio, the full width at half maximum, the phase delay of the two-color pulses, the laser intensity and ionization probability on the harmonic efficiency enhancement were also investigated.
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27

Wang, De-hua. « Photodetachment of the H– ion in a forced harmonic potential ». Canadian Journal of Physics 98, no 9 (septembre 2020) : 883–92. http://dx.doi.org/10.1139/cjp-2019-0482.

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The photodetachment of a H– ion in a forced harmonic potential driven by a general time-dependent oscillating electric field has been investigated in the semi-classical closed orbit theory for the first time. It is found that the driven electric field frequency can affect the photodetachment cross-section of this system greatly. If the frequency of the driving electric field is equal to the harmonic frequency, a resonance phenomenon occurs in the classical motion of the detached electron. The interference effect between the returning electron wave travelling along the closed orbit with the initial outgoing wave gets stronger, causing the photodetachment cross-section to oscillate in a complicated manner. When the frequency of the driving electric field is unequal to the harmonic frequency, the driving electric field can weaken or strengthen the oscillatory structure in the photodetachment cross-section. In addition, the strength and initial phase in the driving electric field can also influence the photodetachment dynamics of the system. Our work provides a new method for controlling the photodetachment of negative ions in a harmonic potential and may guide future experimental research for cavity dynamics or in the ion trap.
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28

Coccia, Emanuele, et Eleonora Luppi. « Time-dependent ab initio approaches for high-harmonic generation spectroscopy ». Journal of Physics : Condensed Matter 34, no 7 (23 novembre 2021) : 073001. http://dx.doi.org/10.1088/1361-648x/ac3608.

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Abstract High-harmonic generation (HHG) is a nonlinear physical process used for the production of ultrashort pulses in XUV region, which are then used for investigating ultrafast phenomena in time-resolved spectroscopies. Moreover, HHG signal itself encodes information on electronic structure and dynamics of the target, possibly coupled to the nuclear degrees of freedom. Investigating HHG signal leads to HHG spectroscopy, which is applied to atoms, molecules, solids and recently also to liquids. Analysing the number of generated harmonics, their intensity and shape gives a detailed insight of, e.g., ionisation and recombination channels occurring in the strong-field dynamics. A number of valuable theoretical models has been developed over the years to explain and interpret HHG features, with the three-step model being the most known one. Originally, these models neglect the complexity of the propagating electronic wavefunction, by only using an approximated formulation of ground and continuum states. Many effects unravelled by HHG spectroscopy are instead due to electron correlation effects, quantum interference, and Rydberg-state contributions, which are all properly captured by an ab initio electronic-structure approach. In this review we have collected recent advances in modelling HHG by means of ab initio time-dependent approaches relying on the propagation of the time-dependent Schrödinger equation (or derived equations) in presence of a very intense electromagnetic field. We limit ourselves to gas-phase atomic and molecular targets, and to solids. We focus on the various levels of theory employed for describing the electronic structure of the target, coupled with strong-field dynamics and ionisation approaches, and on the basis used to represent electronic states. Selected applications and perspectives for future developments are also given.
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29

Liu, H., L. Q. Feng et R. M. Sani. « Effects of inhomogeneous laser field in time and space on the generation of broad spectral continuum and ultrashort attosecond pulse ». Modern Physics Letters B 34, no 13 (28 février 2020) : 2050131. http://dx.doi.org/10.1142/s0217984920501316.

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The inhomogeneous effects of laser field in time and space on the generations of high-order harmonic spectra and attosecond pulses from He atom have been investigated with the assistance of the frequency-chirping technique and the metallic nanostructure. We find that in different combinations of chirps and spatial inhomogeneous effects, not only can the harmonic cutoff be extended, but the single harmonic emission peak (HEP) can also be selected to contribute to the spectral continuum. In detail, with the combinations of (i) symmetric chirp in frequency and positive inhomogeneous effect in space or (ii) asymmetric down chirp in frequency and negative inhomogeneous effect in space, two broad spectral continua with bandwidths of 496 eV and 480 eV can be obtained. Further, by properly adding IR or UV controlling pulse, the harmonic emission efficiency can be enhanced by several orders of magnitude. The enhancement of harmonic yield from adding UV pulse is higher than that from adding IR pulse. Moreover, the difference of harmonic enhancement between UV combined field and IR combined field is much more obvious at lower controlling laser intensity. Through analyzing the ionization probability, we find that the higher enhancement of harmonic yield from UV combined field is because of UV-resonance-enhancement-ionization between the ground state and the excited state of He atom. Finally, by properly superposing some harmonics, a number of attosecond pulses with pulse durations of 45 as can be obtained.
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30

Gevorkyan, Ashot S., et Aleksander V. Bogdanov. « Time-Dependent 4D Quantum Harmonic Oscillator and Reacting Hydrogen Atom ». Symmetry 15, no 1 (16 janvier 2023) : 252. http://dx.doi.org/10.3390/sym15010252.

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With the help of low-dimensional reference equations (ordinary differential equations) and the corresponding coordinate transformations, the non-stationary 4D quantum oscillator in an external field is reduced to an autonomous form. The latter, in particular, reflects the existence of a new type of dynamical symmetry that reduces the equation of motion of a non-stationary oscillator to an autonomous form that does not change with time. By imposing an additional constraint on the wave function of the isotropic oscillator, we have obtained the total wave functions of the reacting hydrogen atom in two different cases: (a) when the non-stationary frequency has two asymptotic values and there is no external field; and (b) when, in addition to the non-stationary frequency, an external force acts on the hydrogen atom. The transition S-matrix elements of various elementary atomic–molecular processes are constructed. The probabilities of quantum transitions of the hydrogen atom to others, including new bound states, are studied in detail, taking into account the influence of external forces.
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31

Kindl, Vladimir, Radek Cermak, Zelmira Ferkova et Bohumil Skala. « Review of Time and Space Harmonics in Multi-Phase Induction Machine ». Energies 13, no 2 (19 janvier 2020) : 496. http://dx.doi.org/10.3390/en13020496.

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Modern multiphase electric machines take advantage of additional degrees of freedom for various purposes, including harmonic current injection to increase torque per ampere. This new approach introduces a non-sinusoidal air gap flux density distribution causing additional technical problems and so the conventional assumptions need to be revised. The paper presents a methodology for synthesis of air gap magnetic field generated by a symmetrically distributed multiphase windings including the rotor field reaction due to the machine’s load. The proposed method is suitable either for single-layer or double layer windings and can be adopted either for full-pitched or chorded winding including slots effects. The article analyses the air gap flux density harmonic content and formulates conclusions important to multiphase induction motors. It also discusses effects of time harmonic currents and illustrates the principle of changing number of pole-pairs typical for harmonic currents being injected to increase torque.
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32

Zhao, Xu. « The Second Harmonic Effect of Fractional-order Azimuthally Varying Vector Optical Field ». Journal of Physics : Conference Series 2242, no 1 (1 avril 2022) : 012002. http://dx.doi.org/10.1088/1742-6596/2242/1/012002.

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Abstract We report for the first time the second-harmonic generation (SHG) of a fractional-order azimuthal varying vector optical field (FO-AVVOF). SHG process is achieved by a Type-II phase-matching BBO crystal. This nonlinear frequency conversion process reveals the topology multiplication rule and obtains the second harmonic optical field of the ultraviolet wavelength, which may have potential applications in ultraviolet micromachining and all-optical switching.
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33

Xu, Xiao-Hu, Yan-Jun Wang et Xiang-Yang Miao. « Theoretical study of high-order harmonic generation from the hydrogen molecular ion with a dichromatic spatially inhomogeneous field ». Modern Physics Letters B 32, no 14 (20 mai 2018) : 1850141. http://dx.doi.org/10.1142/s0217984918501415.

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We theoretically investigate the enhancement of high-order harmonic generation by numerically solving the non-Born–Oppenheimer time-dependent Schrödinger equation from the hydrogen molecular ion in a dichromatic inhomogeneous laser field. An ultrabroad supercontinuum up to 300 orders spectral width is generated. It is found that not only the inhomogeneity, but also the dichromatic field contributes to the significant extension of the harmonic cutoff compared with a monochromatic inhomogeneous laser field. Meanwhile, the long quantum paths can be suppressed and short ones can be enhanced by selecting optimized inhomogeneous parameter [Formula: see text], intensity and carrier envelope phase of the dichromatic inhomogeneous laser field. Furthermore, by superposing a properly selected range of the harmonic spectrum in the continuum region, an isolated 29-as pulse is generated. Both the classical theory and quantum time–frequency analysis are adopted to explain the physical mechanism.
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34

Nassar, Antnio B., et Ruth T. Berg. « Propagator for the time-dependent three-dimensional charged harmonic oscillator in a time-varying magnetic field ». Physical Review A 34, no 3 (1 septembre 1986) : 2462–65. http://dx.doi.org/10.1103/physreva.34.2462.

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35

Feng, Liqiang, et Hang Liu. « High-intensity attosecond X-ray source generation by using low-intensity spatial inhomogeneous mid-infrared pulse combined with an ultraviolet pulse ». International Journal of Modern Physics B 31, no 01 (10 janvier 2017) : 1650239. http://dx.doi.org/10.1142/s0217979216502398.

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We theoretically investigate the high-order harmonic spectra and the attosecond pulse generation from He[Formula: see text] ion driven by the spatial inhomogeneous combined field, consisting of a two-color low-intensity mid-infrared pulse ([Formula: see text] W/cm2) and an ultraviolet (UV) pulse ([Formula: see text] W/cm2). The numerical results show that due to the spatial inhomogeneous effect, the harmonic cutoffs are remarkably extended, and a 986 eV super-continuum can be obtained. Further with the proper introduction of an UV pulse (from 60 nm to 20 nm) to the two-color field, the harmonic yields are enhanced, especially for adding the 30 nm pulse case, a 1113 eV super-continuum (corresponding to a 34.1 dB enhanced field) with less harmonic modulation and six orders of magnitude enhancement can be obtained. Similar calculations have been performed for He atom and an 896 eV super-continuum with four orders of magnitude enhancement can be produced. Time–frequency harmonic distribution and time-dependent electron populations show that the single short quantum path contribution is responsible for the less harmonic modulation and the laser-induced electron excitation is responsible for the harmonic enhancement. Finally, by properly superposing the harmonics, a series of sub-50-as pulses including the whole X-ray region with 3–6 orders of magnitude enhancement can be obtained.
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36

Kress, Rainer. « On the boundary operator in electromagnetic scattering ». Proceedings of the Royal Society of Edinburgh : Section A Mathematics 103, no 1-2 (1986) : 91–98. http://dx.doi.org/10.1017/s0308210500014037.

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SynopsisFor radiating solutions to the time-harmonic Maxwell equations, it is shown that the boundary operator mapping the tangential components of the electric field into the tangential components of the magnetic field is a bounded bijective operator from the space of Holder continuous tangential fields with Hölder continuous surface divergence onto itself.
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37

Chen, Yanzuo, Xuxu Shen, Wendi Lan, Suyu Li, Fuming Guo et Yujun Yang. « The High-Order Harmonic Generation from Atom Driven by Co-Rotating Laser Pulses Composed of Fundamental Frequency and High Frequency ». Symmetry 14, no 3 (3 mars 2022) : 519. http://dx.doi.org/10.3390/sym14030519.

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By numerically solving the time-dependent Schrödinger equation (TDSE), the harmonic generation process of atoms irradiated by corotating laser pulses composed of a fundamental-frequency and high-frequency field is systematically studied. Compared with the harmonic generated from atoms irradiated by counter-rotating two-color circularly polarized laser pulses, the harmonic efficiency of atoms irradiated by co-rotating two-color circularly polarized (CRTCCP) laser pulses with the same laser parameters is higher. The harmonics are generated by the multiphoton radiation transition after the bound electrons undergo a multiphoton absorption transition to a higher energy level. In addition, the variation of the harmonic efficiency with the field strength of different frequency components in the driving laser pulse is also studied. The circularly polarized harmonics with higher intensity can be obtained by optimizing the field strength of the driving laser field.
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38

Qiu, Hongbo, Kaiqiang Hu, Ran Yi et Wei Yanqi. « Effect of high frequency harmonic voltage on the performance of line start permanent magnet synchronous motor ». COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no 2 (4 mars 2019) : 777–92. http://dx.doi.org/10.1108/compel-06-2018-0267.

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Purpose A large number of high-frequency harmonic voltages exist in the output voltage of the inverter, which will affect the performance of the motor. The purpose of this paper is to obtain the influence of high frequency harmonic voltage on the performance of the line start permanent magnet synchronous motor (LSPMSM) and reveal the mechanism of influence. The research results can provide help for the design of LSPMSM driven by inverter drives. Design/methodology/approach First, the actual output voltage data of the inverter is collected, and then the fundamental voltage and high frequency harmonic voltage data can be obtained by performing the fast Fourier transformation method on the voltage data. Second, the finite element model is established. During the finite element calculation, the obtained fundamental voltage and the main harmonic voltage components are used as the voltage source. To research the effect of high frequency harmonic voltage on the performance of motor, a reference group without high frequency harmonic voltage is set up, which is used to compare and analyze the effect of high-frequency harmonics on the performance of the motor. To verify the correctness of the model, a prototype based on the model parameters is manufactured, and then the back EMF experiment and load experiment are performed. The test data and calculation results are compared and analyzed. Findings The coupling relationship between high frequency time harmonic magnetic field and low frequency space harmonic magnetic field is obtained. The stator copper loss and rotor eddy-current loss are calculated and analyzed under normal supply voltage and abnormal supply voltage, and the influence mechanism is revealed Originality/value The coupling relationship between high frequency time harmonic magnetic field and low frequency space harmonic magnetic field is obtained. The sensitivity of the high frequency harmonic voltage to the stator copper loss and rotor eddy-current loss is obtained, and the mechanism of losses change is revealed.
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39

Chen, Duo, et Robert McGough. « Fast calculations of time‐harmonic near field pressure distributions produced by triangular sources ». Journal of the Acoustical Society of America 117, no 4 (avril 2005) : 2560. http://dx.doi.org/10.1121/1.4788520.

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40

DeGersem, H., et T. Weiland. « Field-Circuit Coupling for Time-Harmonic Models Discretized by the Finite Integration Technique ». IEEE Transactions on Magnetics 40, no 2 (mars 2004) : 1334–37. http://dx.doi.org/10.1109/tmag.2004.824536.

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41

While, Peter T., Larry K. Forbes et Stuart Crozier. « A time-harmonic target-field method for designing unshielded RF coils in MRI ». Measurement Science and Technology 16, no 4 (5 mars 2005) : 997–1006. http://dx.doi.org/10.1088/0957-0233/16/4/012.

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42

While, Peter T., Larry K. Forbes et Stuart Crozier. « A time-harmonic target-field method for designing shielded RF coils in MRI ». Measurement Science and Technology 16, no 6 (17 mai 2005) : 1381–93. http://dx.doi.org/10.1088/0957-0233/16/6/021.

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43

Ethem Anar, İbrahim, et Adil Misir. « Far-field patterns for time-harmonic acoustic plane waves in an inhomogeneous medium ». Applied Mathematics and Computation 111, no 1 (mai 2000) : 103–19. http://dx.doi.org/10.1016/s0096-3003(98)10121-2.

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44

Yang, Zhipeng, Xinping Gui, Ju Ming et Guanghui Hu. « Bayesian approach to inverse time-harmonic acoustic scattering with phaseless far-field data ». Inverse Problems 36, no 6 (1 juin 2020) : 065012. http://dx.doi.org/10.1088/1361-6420/ab82ee.

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45

Adly, A. A., et S. K. Abd-El-Hafiz. « An evolutionary computation approach for time-harmonic field problems involving nonlinear magnetic media ». Journal of Applied Physics 109, no 7 (avril 2011) : 07D321. http://dx.doi.org/10.1063/1.3549606.

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46

Liang, Mai-Lin, et Yue Jiang. « Time-dependent harmonic oscillator in a magnetic field and an electric field on the non-commutative plane ». Physics Letters A 375, no 1 (novembre 2010) : 1–5. http://dx.doi.org/10.1016/j.physleta.2010.10.035.

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47

LI, DE-JUN, et YI TANG. « INTERACTIONS BETWEEN THE TIME-VARYING ELECTROMAGNETIC FIELD AND THE QUANTUM SOLITARY WAVE IN A FERROMAGNETIC CHAIN ». Modern Physics Letters B 26, no 24 (21 août 2012) : 1250160. http://dx.doi.org/10.1142/s0217984912501606.

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Starting with the Heisenberg Hamiltonian of the one-dimensional ferromagnetic chain in external fields, we have studied quantum characteristics of solitary waves and interactions between solitary waves and the time-varying electromagnetic field. It is shown that the energy and magnetic moments of the solitary wave are quantized. Utilizing these novel results, we have obtained the Bloch's equation of the two-level quantum solitary wave in a simple harmonic magnetic field.
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48

Chen, Cong, Zhensheng Tao, Carlos Hernández-García, Piotr Matyba, Adra Carr, Ronny Knut, Ofer Kfir et al. « Tomographic reconstruction of circularly polarized high-harmonic fields : 3D attosecond metrology ». Science Advances 2, no 2 (février 2016) : e1501333. http://dx.doi.org/10.1126/sciadv.1501333.

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Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.
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49

Bukhari, Syed Sabir Hussain, Ghulam Jawad Sirewal, Faheem Akhtar Chachar et Jong-Suk Ro. « Dual-Inverter-Controlled Brushless Operation of Wound Rotor Synchronous Machines Based on an Open-Winding Pattern ». Energies 13, no 9 (2 mai 2020) : 2205. http://dx.doi.org/10.3390/en13092205.

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In an open-winding machine, three-phase stator currents can be controlled such that the input armature currents may contain the third-harmonic current component in addition to the fundamental. Considering this attribute of open-winding patterns, a harmonic current field excitation technique for a wound rotor synchronous machine (WRSM) is proposed in this paper based on the control of time-harmonic magneto-motive force. Two inverters connected to both terminals of the stator winding are controlled so that the input armature current generates an additional third-harmonic current component. This third-harmonic component generates a vibrating magnetic field that induces a current in the specially designed rotor harmonic winding. The current is supplied as DC current to the rotor excitation winding to generate a rotor field by using a full-bridge diode rectifier in order to achieve brushless operation. The proposed dual-inverter-controlled brushless operation for a WRSM is executed in ANSYS Maxwell using 2-D finite element analysis to validate its operation and electromagnetic performance.
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50

Aubanel, Eric E., et André D. Bandrauk. « Molecules in strong laser fields : vibrational inversion and harmonic generation ». Canadian Journal of Chemistry 72, no 3 (1 mars 1994) : 673–77. http://dx.doi.org/10.1139/v94-092.

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We examine two consequences of the unique behaviour of molecules in strong fields. First, by time gating of laser-induced avoided crossings with femtosecond laser pulses, one can obtain efficient vibrational inversion into a narrow distribution of vibrational levels of a molecular ion. We demonstrate this by numerical solution of the time-dependent Schrödinger equation for [Formula: see text] Second, we show results of numerical calculation with vibrationally excited [Formula: see text] of harmonic generation up to the 11th order of an intense 1064- nm laser. We predict that competition of photodissociation can be minimized by trapping the molecule in high-field-induced potential wells, thus enhancing the high-order harmonic generation process. Furthermore, the harmonic spectrum can serve as a measure of the structure of these laser-induced potentials.
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