# Seminar khoa hoc

**9.00 AM - 10.00 AM: **Dr.** **Nguyen Hoang Son presents the topic: "Stress-constrained shape and topology optimization using trimmed hexahedral meshes"

Abstract: A trimmed hexahedral mesh is generated at each optimization iteration by cutting a regular hexahedral background mesh with the zero-isosurface of a level set function to minimize a volume with stress constraints. A clear and explicit boundary-conforming mesh can be obtained by using trimmed hexahedral elements placed at the boundary of the solid domain, which leads to an accurate estimation of stresses and shape sensitivities. Since the void domain is not considered in the optimization process, the singularity phenomenon in stress-constrained optimization problems is essentially eliminated without using any relaxation technique.

**10.00 AM – 11.00 AM:** Dr. Le Thi Cam Tu presents the topic: "Wavelength Scaling of High-Harmonic Yield from Co Molecules"

Abstract: Using a longer wavelength is desirable to expand the highest energy photons into XUV regime because of the proportional to the square of the wavelength (λ^2) of the kinetic energy. However, the high harmonic efficiency falls dramatically with increasing wavelength, with a very unfavorable scaling λ −x with x = 5−6 for argon atom [1]. Intensive works on this scaling for atoms and symmetric molecules figure out that x varies with different targets. In this report, we theoretically investigate the harmonic efficiency of asymmetric molecules such as carbon monoxide (CO) driven by intense near-infrared lasers using the time-dependent Schrödinger equation [2].

Reference:

[1] J. Tate et al., Phys. Rev. Lett. 98, 013901 (2007).

[2] C.-T. Le et al., Phys. Rev. A 97, 043405 (2018).

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