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  • Authors: Duc Tu, Vu; Ngoc Minh, Kieu;  Advisor: -;  Co-Author: - (2022)

    We have proposed a fruitful design principle targeting a concentration ratio (CR) >1000× for a typical high concentrating photovoltaics (HCPV) system, on account of a two-concentrator system + homogenizer. The principle of a primary dual-lens concentrator unit, completely analogous basic optics seen in the superposition compound eyes, is a trend not hitherto reported for solar concentrators to our knowledge. Such a concentrator unit, consisting of two aspherical lenses, can be applied to minify the sunlight and reveal useful effects. We underline that, at this stage, the CR can be attained by two orders of magnitude simply by varying the radius ratio of such two lenses known from the optics side. The output beam is spatially minimized and nearly parallel, exactly as occurs in the su...

  • Authors: Vinh V.Le; Thi Hinh, Dinh;  Advisor: -;  Co-Author: - (2022)

    The molecular dynamics simulations have been carried out to investigate the mechanical behaviors of amorphous silicon nitride under the uniaxial tensile deformation. The amorphous silicon nitride was obtained by the cooling process. The network structure of the sample consists of SiNx (x = 3, 4 and 5) units and NSiy (y = 2, 3 and 4) linkages. The stress-strain curve of the sample exhibits the elastic and plastic deformation. The Si-N bond lengths are stretched out in the elastic region and the plastic region I. They are shrunk to the initial state in the plastic region II due to the appearance of the large clusters which contain the overlapping big simplexes with the RS ≥ 2.4 Å. These big simplexes tend to appear at the shear transformation zones in the elastic region. These shear t...

  • Authors: M. Elsisi; Minh-Quang Tran; Vu, Thi Lien; Nguyen, Thi Thanh Nga;  Advisor: -;  Co-Author: - (2022)

    Managing procedure for charging and discharging battery system plays an essential contributor in improving the performance of energy storage system for example increment of utilizing batteries. This paper aims to develop a new hybrid genetic algorithm-based proportional integral (GA-based PI) controller with an adaptive neuro-fuzzy inference system (ANFIS) for the charging balance of batteries. The dataset is generated by using the GA-based PI controller, then a training strategy is introduced for the ANFIS controller. The proposed approach is evaluated by the GA-based PI controller and the PI controller based on Ziegler Nichols method.

  • Authors: Ho, Van Minh Hai; Nguyen, Duc Cuong; Hien Duy, Mai;  Advisor: -;  Co-Author: - (2022)

    The assembly of primary nanoparticles to form hierarchical ultra-porous architectures is of great interest in various fields because of their extremely large surface area and porosity. In this work, the 3D ultra-porous γ-Fe2O3 nanocubes were synthesized by a simple method, which was derived from perfect Prussian Blue nanocubes by the oxidative decomposition process. The as-synthesized 3D γ-Fe2O3 nanocubes possess a large specific surface area and high porosity, which arise from the self-assembly of ultrafine nanoparticles. The 3D ultra-porous γ-Fe2O3 nanocubes-based sensors showed superior detection of acetone and ethanol with excellent sensitivity and rapid response time. The fantastic gas-sensing platform of 3D γ-Fe2O3 nanocubes could originate from their unique structures and int...

  • Authors: Ngo, Trong Hai; V. S. Luong; Ramesh, Chandra Bhatt; Lin-Xiu Ye; Te-ho Wu; Lance Horng; Jong-Ching Wu;  Advisor: -;  Co-Author: - (2022)

    It is commonly known that the coercivity (Hc) of the rare-earth/transition-metal (RE–TM) compound is tuned based on the varying RE content as compared to the TM component. The drawback of this approach is that the Hc changes are permanent. In this work, we investigate the coercivity behaviors of the GdFeCo/Hf/MgO heterostructure where the heavy metal Hf layer is inserted in the middle not only to convert charge current into spin current but also to prevent the oxygen diffusion effect. A strong geometry dependence of coercivity detected on Hall bar devices is attributed to the intrinsic properties of GdFeCo and elucidates that the oxidation issue from MgO on GdFeCo is prevented.

  • Authors: Dung, T. K. Ha; Canh, V. Pham; Huan, X. Hoang;  Advisor: -;  Co-Author: - (2022)

    The field of Submodular Maximization subject to a Knapsack constraint has recently expanded to a variety of application domains, which is facing some challenges such as data explosions or additional conditions. There exist plenty of objective functions that cannot be evaluated exactly in many real cases unless they are estimated with errors. It leads to solving the problem under noise models. Somewhat surprisingly, Submodular Maximization subject to a Knapsack constraint under Noise models (SMKN) has never been discussed a lot before. Hence, in this paper, we consider the problem with two kinds of noise models which are addition and multiplication. Inspired by the traditional Greedy algorithm, we first propose a Greedy algorithm under Noises with provable theoretical bounds. In orde...

  • Authors: Thi Thu Hoai, Bui; Thi Thu Huong, Tran; Dinh Kien, Nguyen;  Advisor: -;  Co-Author: - (2022)

    Geometrically nonlinear behavior of functionally graded (FG) beam and frame structures under mechanical loading is studied in this paper using the finite element method. The structures are made of a mixture of ceramic and metal with material properties varying in the thickness direction by a power distribution law. Based on the first-order shear deformation theory, a nonlinear beam element is derived and used in conjunction with Newton-Raphson method to compute deflected curves of the beams. Numerical investigations are carried out in detail to highlight the influence of the material distribution on the nonlinear behavior of the beams.

  • Authors: Chao, Xu; Thien, Van Luong; Luping, Xiang; Shinya, Sugiura; Robert, G. Maunder; Lie-Liang, Yang; Lajos, Hanzo;  Advisor: -;  Co-Author: - (2022)

    A variety of deep learning schemes have endeavoured to integrate deep neural networks (DNNs) into channel coded systems by jointly designing DNN and the channel coding scheme in specific channels. However, this leads to limitations concerning the choice of both the channel coding scheme and the channel paramters. We circumvent these impediments and conceive a turbo-style multi-carrier auto-encoder (MC-AE) for orthogonal frequency-division multiplexing (OFDM) systems, which is the first one that achieves the flexible integration of DNN into any given channel coded systems while achieving an iteration gain. More explicitly, first of all, we design the MC-AE independently of both the channel coding arrangement and of the channel model, where the output layer of the MC-AE decoder is des...