Le Quy Don Technical University

About: Le Quy Don Technical University is a education organization based out in Hanoi, Vietnam. It is known for research contribution in the topics: Band gap & Relay. The organization has 933 authors who have published 1335 publications receiving 8955 citations. The organization is also known as: Le Quy Don University of Science and Technology & Military Technical Academy.

Landslide susceptibility modeling using Reduced Error Pruning Trees and different ensemble techniques: Hybrid machine learning approaches

Abstract: Nowadays, a number of machine learning prediction methods are being applied in the field of landslide susceptibility modeling of the large area especially in the difficult hilly terrain. In the present study, hybrid machine learning approaches of Reduced Error Pruning Trees (REPT) and different ensemble techniques were used for the construction of four novel hybrid models namely Bagging based Reduced Error Pruning Trees (BREPT), MultiBoost based Reduced Error Pruning Trees (MBREPT), Rotation Forest-based Reduced Error Pruning Trees (RFREPT), Random Subspace-based Reduced Error Pruning Trees (RSREPT) for landslide susceptibility assessment and prediction. In total, ten topographical and geo-environmental landslide conditioning factors were considered for analyzing their spatial relationship with landslide occurrences. Receiver Operating Characteristic curve, Statistical Indexes, and Root Mean Square Error methods were used to validate performance of these models. Analysis of model results indicate that the BREPT is the best model for landslide susceptibility assessment in comparison to other models.

Layered graphene/GaS van der Waals heterostructure: Controlling the electronic properties and Schottky barrier by vertical strain

Abstract: In this work, we construct an ultrathin graphene/GaS heterostructure and investigate its electronic properties as well as the effect of vertical strain using density functional theory. The calculated results of the equilibrium interlayer spacing (3.356 A) and the binding energy show that the intrinsic properties of isolated graphene and GaS monolayers can be preserved and the weak van der Waals interactions are dominated in the heterostructures. The van der Waals heterostructure (vdWH) forms an n-type Schottky contact with a small Schottky barrier height of 0.51 eV. This small Schottky barrier height can also be tuned by applying vertical strain. Furthermore, we find that the n-type Schottky contact of the vdWH can be changed to p-type when the interlayer spacing is decreased and exceeded to 2.60 A. These findings show the great potential application of the graphene/GaS vdWH for designing next generation devices.

On the high temperature mechanical behaviors analysis of heated functionally graded plates using FEM and a new third-order shear deformation plate theory

Abstract: Composite functionally graded materials (FGMs) are fabricated and most commonly used to operate in high temperature environments, where are expected to have significant changes in properties of constituent materials. The FGMs inherently withstand high temperature gradients due to low thermal conductivity, core ductility, low thermal expansion coefficient, and many others. It is essential to thoroughly study mechanical responses of FGMs and to develop new effective approaches for accurate prediction of solutions. We present in this paper new numerical results of high temperature mechanical behaviors of heated functionally graded (FG) plates, emphasizing the high temperature effects on static bending deflections and natural frequencies. A displacement-based finite element formulation associated with a novel third-order shear deformation plate theory (TSDT) without any requirement of shear correction factors is thus developed, taking the desirable properties and advantages of the TSDT theory as its kinematics of displacements are derived from elasticity theory rather than the hypothesis of displacement. The FG plates are assumed to be placed suffering high temperature environment, resulting in a uniform distribution of temperature across the plate thickness. The variation of material compositions across the thickness is described by a power-law distribution. Representative numerical examples of heated FG plates with different shapes are considered and obtained results are then investigated. The work additionally involves parametric studies performed by varying volume fraction, temperature range, material combinations, thickness-to-length ratio, etc., which have significant impacts on mechanical deflections and natural frequencies of heated FG plates. It is found that the ZrO2/SUS304 plate possesses different static bending behaviors and performance compared to Al2O3/SUS304 and Si3N4/SUS304 plates due to the differences not only in the nonlinear thermal expansions but also in the material behaviors of constituent materials. In the contrary similar behaviors of natural frequencies of all FG plates is found.

Palladium nanoparticles immobilized on core-shell magnetic fibers as a highly efficient and recyclable heterogeneous catalyst for the reduction of 4-nitrophenol and Suzuki coupling reactions

Abstract: In this study, a novel core–shell magnetic fibrous nanocatalyst, Pd/Fe3O4@SiO2@KCC-1 with easily accessible active sites and a convenient recovery by applying an external magnetic field, was successfully developed. Fe3O4@SiO2@KCC-1 was functionalized with amino groups which act as robust anchors so that the palladium nanoparticles (Pd NPs) with an average diameter of about 4 nm were well-dispersed on the fibers of Fe3O4@SiO2@KCC-1 without obvious aggregation. The synthesized Pd/Fe3O4@SiO2@KCC-1 nanocatalyst exhibited excellent catalytic activity in the reduction of 4-nitrophenol by sodium borohydride, and the Suzuki cross coupling reactions of aryl chlorides with aryl boronic acids due to the easy accessibility of the active sites. Furthermore, the Pd/Fe3O4@SiO2@KCC-1 nanocatalyst was conveniently recovered by a magnet and could be reused for at least five cycles without significant loss in activity, thus confirming its good stability. Therefore, the abovementioned approach based on core–shell magnetic fibrous Fe3O4@SiO2@KCC-1 provided a useful platform for the fabrication of Pd NPs based catalysts with easy accessibility, superior activity and convenient recovery.