arXiv subjects

Li Hang

Publications and source records attributed to Li Hang.

3 recordsLinked to original sources

arXiv2025

Error analysis of a Euler finite element scheme for Natural convection model with variable density

In this paper, we derive first-order Euler finite element discretization schemes for a time-dependent natural convection model with variable density (NCVD). The model is governed by the variable density Navier-Stokes equations coupled with a parabolic partial differential equation that describes the evolution of temperature. Stability and error estimate for the velocity, pressure, density and temperature in $L^2$-norm are proved by using finite element approximations in space and finite differences in time. Finally, the numerical results are showed to support the theoretical analysis.

math.NA↗

arXiv2019

Optical needles with arbitrary homogeneous three-dimensional polarization

We propose a new method to generate optical needles by focusing vector beams comprised of radially polarized component and azimuthally polarized vortex components. The radial part can generate longitudinal polarization, while the azimuthal parts can generate left- and right-handed polarization. Hence, an arbitrary 3D polarization can be obtained. To our knoeledge, it may be the first time that arbitrarily polarized optical needles whose transverse sizes are under 0.5$λ$ have been achieved. And their polarized homogeneity is beyond 0.97.

physics.optics↗

arXiv2013

Corrections on energy spectrum and scatterings for fast neutron radiography at NECTAR facility

Neutron spectrum and scattered neutrons caused distortions are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM-II in Technische Universität München (TUM), Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by neutron spectrum, as well as the Point Scattered Function (PScF) simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve images qualities. Good analysis results prove the sounded effects of above two corrections.

physics.ins-det↗