Seminar khoa học của TS. Nguyễn Thành Nhơn và TS. Hoàng Lê Thụy Thùy Trang

Vào 13h30 ngày 15/9/2023, Viện IAST tổ chức buổi trao đổi học thuật tại Phòng họp B với nội dung chi tiết như sau: 

TS. Nguyễn Thành Nhơn trình bày về "A multigrid coupling approach of the extended isogeometric-meshfree method and peridynamics for brittle fracture"

Abstract: A multigrid coupling approach involving the extended isogeometric-meshfree (XIMF) method and bond-based peridynamics (PD) has been developed for static and dynamic fracture problems. This coupling approach leverages the advantages of both the XIMF method and PD, including the generality of PD in dealing with fracture problems and the computational efficiency of the XIMF method. To couple these two methods, the problem domain is divided into two subdomains: peridynamic and isogeometric-meshfree. The first subdomain, designed to model both the crack-tip and potential cracking zones, is discretized using fine peridynamic points. The latter corresponds to the remaining zone and is discretized using coarse isogeometric-meshfree meshes. These two subdomains are connected by interface meshes, where ghost peridynamic particles are embedded, and displacement constraints are enforced. This approach allows us to capture fracture patterns without the need for complex crack-tip enrichment functions in three dimensions, while maintaining the computational efficiency of the XIMF method. Furthermore, we propose an adaptive switching strategy to convert isogeometric-meshfree meshes into peridynamic particles. Finally, we validate this approach by tackling several representative benchmark problems, including the static crack propagation and dynamic crack branching.

TS. Hoàng Lê Thụy Thùy Trang trình bày về "Synthesis and Catalytic Activity of Silver Nanoparticles Embedded on Layered Double Hydroxides"

Abstract: Silver nanoparticles (AgNPs) embedded on layered double hydroxides (LDH) was synthesized by simply mixing the preformed AgNPs colloids with the as-prepared solid support. The abundant surface hydroxyl groups of LDH were exploited to form H-bonds with carboxylates-capped AgNPs. Spectroscopic and electron microscopic characterization studies revealed the highly dispersed AgNPs on LDH. The silver contents in the products obtained were found to depend on the availability of hydroxyl groups in the solid supports. The highest silver content was obtained when using reconstructed LDH that was previously calcined at 450 °C. The catalytic activity of the products was evaluated in the reduction of 4-nitrophenol. The rate constants of the 4-nitrophenol reduction catalyzed by Ag/LDH were about 2.5 times higher than that of pure AgNPs. The catalytic activity of materials was found to improve with the increase of silver content and reach the maximum value at 4 wt% Ag. Moreover, the decrease in particle size of AgNPs was another factor to enhance their catalytic activity.