Nhan Thinh Hoang

This study presents a nonlinear dynamic analysis of functionally graded half-cylinder sandwich (FGhCS) shells with elastic boundary conditions (EBCs) subjected to explosive loading (EL). An efficient finite element framework is developed based on a novel first-order shear deformation theory (n-FSDT) to account for both geometric and material nonlinearities. The governing equations are systematically derived from Hamilton’s principle, incorporating large deformation effects through von Kármán-type kinematics. The proposed model is validated against benchmark solutions, demonstrating high accuracy and improved computational efficiency. Parametric investigations are performed to assess the influences of geometric characteristics, material gradation, and boundary stiffness on the dynamic response. The results reveal that appropriate material distribution and elastic restraints can effectively mitigate the adverse effects of explosive loads, providing valuable insights for the optimal design of sandwich shell structures.

The main goal of this study is to extend the isogeometric analysis (IGA) further to investigate the free vibration of graphene platelet (GPL)-reinforced functionally graded triply periodic minimal surface (FG-TPMS) nanoplates (so-called GPLR-FG-TPMS nanoplates) embedded in Pasternak foundation (PF). The computational model includes both nonlocal elasticity and strain gradient effects to account for the impact of small-size effects inherent in nanostructures. To achieve C1-continuity condition, an IGA framework based on HSDT is developed with 7-DOFs per a control point. The motion equation of the nanoplate is derived from Hamilton's principle. The calculation program is coded in Matlab environment and verified through comparative examples. From here, the influence of geometric parameters, material properties, and boundary conditions (BCs) on the frequency of nanoplates is investigated in detail. The results obtained are reference materials for further studies as well as in the calculation and design of GPLR-FG-TPMS structures in practice.

This study presents an enhanced finite element method (FEM) integrated with the improved first-order shear deformation theory (i-FSDT) for analyzing the natural frequencies of functionally graded sandwich (FGSW) plates resting on a variable elastic foundation (VEF) with uncertain input parameters. The FGSW plates are composed of two functionally graded (FG) face layers and a homogeneous or FG core layer. The proposed method is validated by comparing it with existing benchmark solutions to ensure its accuracy and reliability. In addition, the study explores the effects of geometric configurations, material properties, foundation types, and boundary conditions (BCs) on the natural frequencies of FGSW plates. To address uncertainty in input parameters, Monte Carlo simulation (MCS) is employed to determine the probabilistic range of natural frequencies. The numerical and graphical results show that the uncertainties of the input parameters interact to greatly affect the natural frequency of sandwich plates.

The (Ba,Ca)ScO2F:Bi3+,K+ phosphor with narrow emission band and green emission color peaking at 510 nm is demonstrated in the study. This phosphor is prepared using a solid-state reaction at high temperatures. Based on characterizing data, the increasing concentration of Ca2+ induces the shrinkage of the unit cell and the narrower spacing, leading to the increase in the photoluminescence of the phosphor. This also cause a red shift in the emitting range from 504 nm to 510 nm. The phosphor shows good absorption peaking at 415 nm, matching the excitation wavelength of the used nearultraviolet (UV) light emitting diode (LED) chip. When being applied in a white light‐emitting diodes (WLED) with 4,000 K, the phosphor could increase the luminous flux as its doping concentration increase. Besides, the WLED doping (Ba, Ca) ScO2F: Bi3+, K+ shows emission regions in blue, green, and red wavelength bands. The data from the study indicates that the phosphor is potential for developing the white-LED for backlight purposes.

The optimal spectral characteristics and photometric qualities in white-emitting light-emitting diodes (WLEDs) featuring red-emitting LEDs instead of phosphor (pc/R-WLEDs) were determined using the luminescent efficiency (LE) theory. The color quality scale (Rf) is higher than 97K for correlating color temperature (CCTs) ranging between 2700K and 6500K. We first identified genuine pc/R-WLEDs having Rf levels at 96–97, LE levels at 120–124 lm/W with CCT levels at 2969K, 4468K, 5682K, as well as 6558K with the utilization of all four-color phosphors: blues (448 nm), reddish (650 nm) LEDs, greenish (507 nm), and yellowish (586 nm). When compared to phosphorus-converted white-emitting LEDs (pc-WLEDs) and quantum dots white-emitting LEDs (QD-WLEDs), the pc/R-WLEDs, rather than the QD-WLED, would make better representatives of improved color version, notably in the reduced color temperatures, and could eventually replace current pc-WLEDs.

Sr3Al2O5Cl2:Bi3+ (SAlOCl:Bi3+)phosphor for broadband emission was made using a solid-state method. From the extensive spectroscopic analysis and theoretical computation, significant conclusions about the origin of the Bi3+ emission were drawn. For the Sr 3 and Sr 1 sites, respectively, the dipole-quadrupole and quadrupole-quadrupole interactions were responsible for the concentration quenching in SAlOCl:Bi3+. The resulting luminescence mechanism demonstrated that the crystallization of Bi3+ at the two sites is what causes the emission from each site. The warm white light emitting diodes (LED) models were built with a 380-nm ultraviolet (UV) chip, SAlOCl:Bi3+, and two other phosphors. Then, the color rendering indeces (CRI) and the correlated color temperature (CCT) were calculated. Particularly, the CRI values ranged from 84.3 to 86.2 under operating currents of 20–50 mA, respectively. The increasing SAlOCl:Bi3+ dosage also heightened particle density, resulting in higher scattering coefficients. High scattering results in improved color coordination (lower color variance). The CRI and luminous flux are reduced as the phosphor SAlOCl:Bi3+ concentration increases more than owing to color loss and energy loss by backscattering and re-absorption. Thus, it is advisable to consider SAlOCl:Bi3+ carefully before applying in production.

Sr3Al2O5Cl2:Bi3+ (SAlOCl:Bi3+)phosphor for broadband emission was made using a solid-state method. From the extensive spectroscopic analysis and theoretical computation, significant conclusions about the origin of the Bi3+ emission were drawn. For the Sr 3 and Sr 1 sites, respectively, the dipole-quadrupole and quadrupole-quadrupole interactions were responsible for the concentration quenching in SAlOCl:Bi3+. The resulting luminescence mechanism demonstrated that the crystallization of Bi3+ at the two sites is what causes the emission from each site. The warm white light emitting diodes (LED) models were built with a 380-nm ultraviolet (UV) chip, SAlOCl:Bi3+, and two other phosphors. Then, the color rendering indeces (CRI) and the correlated color temperature (CCT) were calculated. Particularly, the CRI values ranged from 84.3 to 86.2 under operating currents of 20–50 mA, respectively. The increasing SAlOCl:Bi3+ dosage also heightened particle density, resulting in higher scattering coefficients. High scattering results in improved color coordination (lower color variance). The CRI and luminous flux are reduced as the phosphor SAlOCl:Bi3+ concentration increases more than owing to color loss and energy loss by backscattering and re-absorption. Thus, it is advisable to consider SAlOCl:Bi3+ carefully before applying in production.