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  • Authors: Pham, Kim Ngoc; Trung, Kien Mac; Huu, Tuan Nguyen;  Advisor: -;  Co-Author: - (2022)

    In the present work, we have reported the dye removal efficiency of Cobalt chromite, CoCr2O4 nanoparticles synthesized via the solvothermal method. The obtained CoCr2O4 nanoparticles demonstrated that the dye removal efficiency of CoCr2O4 nanoparticles could be enhanced by a reduction of size or improved water dispersibility. The pseudo-second-order kinetic model best describes the adsorption of Congo red (CR) dye on CoCr2O4 nanoparticles. The Langmuir adsorption isotherm model fitted best for the adsorption process and the adsorption capacity for CCO@450 and CCO@550 nanoparticles were found to be 59.4 and 43.8 mg g−1, respectively. Dye adsorption studies on a mixture of CR, MB, and RhB dyes solution revealed that the MB removal efficiency of CoCr2O4 nanoparticles could improve to 8...

  • Authors: Vinh-Hung Tran; Tat-Tai Truong; Khac-Khanh Bui; Hong-Ky Le;  Advisor: -;  Co-Author: - (2022)

    Mechanical elements with freeform surfaces are very common in aerospace, automotive, mold and die industries. With increasing demand for higher quality of freeform surfaces in many different applications, quality monitoring and evaluation of freeform surfaces have become of great concern in modern manufacturing. In this study, quality evaluation of a freeform surface manufactured by CNC milling was carried out. First, the point cloud data of a given freeform surface sample manufactured by stamping were acquired by using different scanning systems, namely HandySCAN 3D 700 and ATOS Compact Scan 5M. Based on the point cloud data, the toolpaths, including roughing, semi-finishing, and finishing, were generated using computer-aided manufacturing (CAM) software. Milling experiments were t...

  • Authors: Nguyen, Tuan Anh; Nguyen, Ngoc Huyen; Ngo, Xuan Dinh;  Advisor: -;  Co-Author: - (2022)

    In this study, we have investigated the influence of crystallinity, phase ratio, and heterojunction formation on the sensing performance of ZnO/ZnFe2O4 (ZnO/ZFO) nanocomposite-based electrochemical sensors for the detection of furazolidone (FZD) antibiotic drug. Results obtained show that the crystallinity and phase ratio of ZnO/ZFO nanocomposites have decisive effects on their electron transfer and active site density. Tuning the crystallinity and ZnO content of ZnO/ZFO nanocomposites is an effective way to enhance the FZD electrochemical sensing performance. Findings from this research suggested that the formation of ZnO/ZFO heterojunction could significantly improve their electrochemical responses for FZD due to arising of the internal electric field and redistribution of Zn2+, F...

  • Authors: Huan Thanh, Duong; Hieu Chi, Phan; Tien Thinh, Le;  Advisor: -;  Co-Author: - (2022)

    Functionally Graded Materials (FGM) is the advanced material that covers the advantages of both metal and ceramic which contain FGM. Due to the perfect combination, FGM plate is widely developed with the requirement for the practical application to avoid the difficulties from conventional approaches. Consequently, the study establishes the database from analytical model and uses it for developing a machine learning model in the desire of finding an alternative model to predict critical buckling load of the plate. Such a machine learning model is crucial for predicting critical buckling load of the FGM plate without complexity of analytical developments or finite element resources. The Gaussian Process Regression model has been developed based on the database containing 1000 labeled ...

  • Authors: Cao, H. Nam;  Advisor: -;  Co-Author: - (2022)

    By applying the island rule proposed recently, we compute the entanglement entropy of Hawking radiation and study the Page curve for the eternal black holes in massive gravity. We investigate for both the neutral and charged black holes which the corresponding results of Schwarzschild and Reissner–Nordström black holes are restored in the limit of massless graviton. We show for the neutral and non-extremal charged black holes that the island is not formed at the early times of the evaporation and hence the entanglement entropy increases linearly in time. However, for the extremal charged black hole, the calculation of the entanglement entropy at the early times without the island is ill-defined because the metric is divergent at the curvature singularity. This implies that new physi...

  • Authors: David, Wai Lun Ng; Abel, Duarte Alonso; Alessandro, Bressan;  Advisor: -;  Co-Author: - (2022)

    The purpose of this study is to build an understanding of how firms operate under the COVID-19 crisis. Specifically, the study examines the significance of firms’ survival for their surrounding community, business–community relations during this severe situation and factors helping firms address this unprecedented challenge. The conceptual tenets of stakeholder theory are considered.

  • Authors: Duong Thi Ha*, Dinh Ngoc Dzung, Nguyen Van Ngoc, Bui Son Tung, Thanh Son Pham, YoungPak Lee, Liang Yao Chen, Bui Xuan Khuyen and Vu Dinh Lam;  Advisor: -;  Co-Author: - (2021)

    We demonstrate a multifunctional metamaterial (MM) structure which can behave like a perfect absorber (PA) or polarization converter (PC) by controlling the lumped varactor. In PC mode, the MM revealed cross-polarization conversion in a frequency range from 2.0 to 7.0 GHz with a polarization-conversion ratio of nearly 100%. While in the PA state, triple-band high absorption was achieved. In addition, we investigated numerically the PA and PC modes by scaling down the geometrical dimension and orientation of the proposed unit cells, for further development of innovative methods in the THz range. Our work is expected to contribute to the realization of future multifunctional MM-based devices working in the GHz or higher-frequency range.

  • Authors: Kien.Nguyen Trung;  Advisor: -;  Co-Author: - (2021)

    Improving engine power density by using supercharging system with exhaust gas energy recovery (called an exhaust gas turbocharger) is a trend of improving non-turbocharged base engines in Vietnam. These engines are still capable of being used for a considerable time, but the power generating is not big enough to meet the requirements of improving vehicle maneuverability, especially special vehicles such us Russian or Vietnamese tanks. To determine the maximum level of pressure ratio of the engine according to the engine thermal load criteria, we can use direct and indirect indicators. The content of the paper is to determine the heat flow density for cooling water in the V12 engine according to the different pressure ratios. From that, the maximum level of pressure ratio for the eng...

  • Authors: Nguyen, Khong Van; Vu, Le Anh; Thoan Tran, Van; Trung, Tran Anh; Vu, Nguyen Hoang;  Advisor: -;  Co-Author: - (2022)

    Research, development and application of alternative fuels are common approaches in many countries around the world to reduce dependence on fossil fuels, to improve energy security as well as to decrease environmental pollution such as the greenhouse gas emission. The use of biodiesel fuels as an alternative fuel for petroleum diesel fuel is very effective for the reduction of CO2 emission, because biodiesel is produced from renewable biomass resources. However, there are a few of the using biodiesel research on CRDI (Common Rail Direct Injection) diesel engine. This paper describes a real time CRDI diesel engine 2.5TCI-A HYUNDAI STAREX simulations with blends of palm oil derived biodiesel and diesel using Matlab simulink software. The results show small deviation from cylinder pres...