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"On the problem of the densest packing of spherical segments into a sphere Sobre o problema do empacotamento mais denso de segmentos esféricos em uma esfera"

( 2023)
Duc Thinh Vu, The Bao Phung, A.A. Lempert, Duc Minh Nguyen.

"The paper considers a particular variant of the classical optimal packing problem when the container is a sphere, the packed elements are equal spherical caps, and the optimality criterion is to maximize their geodesic radius. At the same time, we deal with a special integral metric to determine the distance between points, which becomes Euclidean in the simplest case. We propose a heuristic numerical algorithm based on the construction of spherical Voronoi diagrams, which makes it possible to obtain a locally optimal solution to the problem under consideration. Numerical calculations show the operability and effectiveness of the proposed method and allow us to draw some conclusions about the properties of packings."
Formation of pyramidal structures through mixing gold and platinum atoms: the AuxPty2+ clusters with x + y = 10†

( 2023)
Bao Ngan Nguyen Ha, Cam Tu Phan Dang, Long Van Duong, My Phuong Pham Ho, Minh Tho Nguyen, Nguyen Minh Tam

The geometric and electronic structures of a small series of mixed gold and platinum AuxPty2+ clusters, with x + y = 10, were investigated using quantum chemical methods. A consistent tetrahedral pyramid structure emerges, displaying two patterns of structural growth by a notable critical point at y = 5. This affects the clusters' electron population, chemical bonding, and stability. For the Pt-doped Au clusters with y values from 2 to 5, the bonds enable Pt atoms to assemble into symmetric line, triangle, quadrangle, and tetragonal pyramidal Pty blocks, respectively. For the Au-doped Pt clusters, with larger values of y > 5, the structures are more relaxed and the d electrons of Pt atoms become delocalized over more centers, leading to lower symmetry structures. A certain aromaticity arising from delocalization of d electrons over the multi-center framework in the doped Pt clusters contributes to their stability, with Pt102+ at y = 10 exhibiting the highest stability. While the ground electronic state of the neutral platinum atom [Xe]. 4f145d96s1 leads to a triplet state (3D3), the total magnetic moments of AuxPty2+ are large increasing steadily from 0 to 10 μB and primarily located on Pt atoms, corresponding to the increase of the number of Pt atoms from 0 to 10 and significantly enhancing the magnetic moments. An admixture of both Au and Pt atoms thus emerges as an elegant way of keeping a small pyramidal structure but bringing in a high and controllable magnetic moment.
A NURBS-based IGA using zig-zag plate theory for nonlinear passive/semi-active damping analysis of laminated FG-CNTRC plates

( 2023)
T. Nguyen-Thoi, Duy-Khuong Ly, Sy-Ngoc Nguyen, Vinyas Mahesh, Chanachai Thongchom

"In this article, a novel numerical approach based on electromechanical coupling isogeometric analysis employing a piecewise linear zig-zag function is proposed for modeling and analysis of smart constrained layer damping (SCLD) treatment in multilayer porous functionally graded graphene platelets-reinforced composite (PFG-GPRC) plates. The approach efficiently approximates the geometric, mechanical, and electric displacement fields by utilizing non-uniform rational B-splines (NURBS) basis functions. These basis functions are subsequently integrated with the zig-zag formulation to characterize the system dynamic and help handle both continuous/discontinuous material properties at all interfaces, as well as improve the effectiveness of global–local numerical solutions for the analysis of current structures. The multilayer PFG-GPRC plate model is designed to incorporate porous, uniformly, or non-uniformly distributed layers based on three different graphene platelet patterns. The analysis of the SCLD treatment encompasses an examination of the frequency response function of the damped structure under passive/hybrid mechanisms, taking into account"
An electromechanical coupling isogeometric approach using zig-zag function for modeling and smart damping control of multilayer PFG-GPRC plates

( 2023)
"T. Nguyen Thoi , Duy-Khuong Ly, S. Kattimani Chanachai Thongchom"

"In this article, a novel numerical approach based on electromechanical coupling isogeometric anal ysis employing a piecewise linear zig-zag function is proposed for modeling and analysis of smart constrained layer damping (SCLD) treatment in multilayer porous functionally graded graphene platelets-reinforced com posite (PFG-GPRC) plates. The approach efficiently approximates the geometric, mechanical, and electric displacement fields by utilizing non-uniform rational B-splines (NURBS) basis functions. These basis func tions are subsequently integrated with the zig-zag formulation to characterize the system dynamic and help handle both continuous/discontinuous material properties at all interfaces, as well as improve the effective ness of global–local numerical solutions for the analysis of current structures. The multilayer PFG-GPRC plate model is designed to incorporate porous, uniformly, or non-uniformly distributed layers based on three different graphene platelet patterns. The analysis of the SCLD treatment encompasses an examination of the frequency response function of the damped structure under passive/hybrid mechanisms, taking into account"
MULTI-TASKING LEARNING FOR THE PROBLEM OF DETERMINING THE POSITION AND DIRECTION OF PERSON AT THE TIME

( 2023)
Trà Văn Đồng , Nguyễn Thu Nguyệt Minh , Lý Hải Sơn

With many practical applications print human life today such as manufacturing surveillance cameras, analyzing and processing customer behavior, ..., the problem of face detection and head pose estimation on digital images is being noticed by many researchers. A large number of proposed deep learning models have state-of-the-art accuracies such as YOLO, SSD, and MTCNN, solving the problem of face detection or HopeNet, FSA-Net, and RankPmodelsodel used for head pose estimation problems.According to bigmany state-of-the-artmethods, the process of this task consists of 2 parts face detection to head pose estimation. These two steps are completely independent and do not share information with each other. This makes the model clear print setup but does not leverage most of the featured resources extracted in each model. In this thesis, we proposed the PoseMultitask model with the motivation to leverage the features extracted from the face detection model, sharing them with the head pose estimation branch to improve accuracy. Also, with the variety of data, the Euler angle domain representing the face is large, our model can predict results in the 360° Euler angle domain. Applying the multi-tasking learning method, the PoseMultitask model can simultaneously predict the position and direction of the human head. To increase the ability to predict the head direction of the model, we change the representation of the human face from the rom Euler angle to vectors from the Rotation matrix.