A new method called the SO-DGTD method is proposed for solving the time-dependent Maxwell's equations via the Discontinuous Galerkin Time Domain (DGTD) method with dispersive media, the Shift Operator (SO) method is used to represent the constitutive relations. This method has a universal equation for dispersive media models, i.e. the Debye model, the Drude model, the Lorentz model, the SO-DGTD method can be applied to the hybrid dispersive media model. The accuracy of the proposed method is verified by numerical examples.
A CFD method of studying valve timing was introduced,and it was used for studying the valve timing of a diesel engine.Different valve-timing schemes under four running conditions were evaluated;inducted air and scavenged air were quantified and the amount of inlet backflow and trapped air in cylinder was analyzed at different inlet advanced angle.The results show that the CFD method can be used as an effective way for determining valve timing of variable valve timing system,variable camshaft system and even non-cam driven valve system.
According to the Lighthill-Curle sound analogy theory, the aerodynamic noise source arising from automobile in moving mainly comes from the surface dipole source which is determined by the turbulence pressure fluctuation near the vehicle surface, and its strength & distribution determine the external aerodynamic acoustic field around the automobile. This paper focuses on the prediction of aerodynamic dipole acoustics source distribution on automobile surface with the help of CFD technology combined with BEM method. Then the external acoustic field outside the automobile could be simulated based on aerodynamic dipole acoustics source.
In the framework of the generalized Lorenz–Mie theory (GLMT), the optical force and torque on a graphene-coated gold nanosphere by a vector Bessel beam are investigated. The core of the particle is gold, whose dielectric function is given by the Drude–Sommerfeld model, and the coating is multilayer graphene with layer number N, whose dielectric function is described by the Lorentz–Drude model. The axial optical force Fz and torque Tz are numerically analyzed, and the effects of the layer number N, wavelength λ, and beam parameters (half-cone angle α0, polarization, and order l) are mainly discussed. Numerical results show that the optical force and torque peaks can be adjusted by increasing the thickness of the graphene coating, and can not be adjusted by changing α0 and l. However, α0 and l can change the magnitude of the optical force and torque. The numerical results have potential applications involving the trapped graphene-coated gold nanosphere.
DDA method is used to compute scattering properties of various cube-shaped particles induced by different kinds of Airy light-sheets. The effects of modulation parameter, transverse scale and beam center of the beam sheet to scattering, absorption, and extinction cross-sections are investigated in this paper.
As the tweezer light sources, single beam optical traps, have become a kind of important tool for non-contact manipulation of microscopic objects. The interaction of light-sheets with objects allows flow visualization, nondestructive optical sectioning and imaging of the internal subcellular features. In the framework of GLMT, based on the vector angular spectrum decomposition method, with the Lorenz gauge condition and Maxwell's equations allow adequate determination of the Cartesian components of the incident radiated electric field components. The Bessel pincer light-sheets with characteristics of auto-focusing and self-bending, has great advantages in non-destructive optical sectioning and imaging of the internal subcellular features. The influences of the Bessel pincer light-sheets (mainly focusing on beam order and scaling parameter) acting on a dielectric sphere particle, will be discussed. The results will show the sensitivity of beam parameters (beam order and scaling parameter) to the radiation force and the negative force. Further, the present solution can be used to calculate the optical torque, which is of great importance in particle transport and rotation.
Based on the optical Magnus effect, the analytical expressions of the electromagnetic field that a spinning dielectric sphere illuminated by polarized plane waves are derived according to the "instantaneous rest-frame" hypothesis and Minkowski’s theory. More attention is paid to the near field. The unusual optical phenomena in mesoscale spheres without material and illumination wave asymmetry that are the photonic hook (PH) and whispering gallery mode (WGM)-like resonance caused by rotation are explored. The impact of resonance scattering on PHs is further analyzed under this framework. The influence of non-reciprocal rotating dimensionless parameter γ on PH and resonance is emphasized. The results in this paper have extensive application prospects in mesotronics, particle manipulation, resonator design, mechatronics, and planetary exploration.
Laser diodes (LDs) are widely used in optical wireless communication (OWC) and optical networks, and proper theoretical models are needed to precisely describe the complicated beam field of LDs. A novel mathematical model is proposed to describe the vectorial field of nonparaxial LD beams. Laser beam propagation is studied using the vector Rayleigh diffraction integrals, and the stationary phase method is used to find the asymptotic expansion of diffraction integral. The far-field distribution of the LD beam in the plane parallel and perpendicular to the junction is considered in detail, and the computed intensity distributions of the theory are compared with the corresponding measurements. This model is precise for single transverse model beam of LDs and can be applied to describe the LD beams in OWC and optical networks.
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