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Hai Le Xuan,Quoc-Dong Hoang,Soon Geul Lee,Dat Pham Xuan,Hoang Tran Viet,Minh Pham Van,Hung Pham Van,Hung Pham Viet,PHAM DUC TUAN,Duc Anh Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2
Ballbots, which have been studied for over ten years, are under-actuated mobile robots that operate using the inverted pendulum paradigm. Controlling a ballbot poses a number of challenges, including maintaining the stable upright posture from the ground in all directions and making sure it follows the desired trajectory. External factors such as a minor change in contact surface properties or fabrication errors can affect the system's stabilization and transfer capabilities. In this study, an adaptive hierarchical sliding mode control algorithm based on an artificial neural network is developed to make the ballbot robust to external factors. The use of the proposed controller ensures system stability despite uncertainties including friction, accidental centrifugal forces and gravity that occur when the ballbot follows the reference trajectory. The system stability is guaranteed on the basis of Lyapunov theory. Control efficiency and robot stability under system uncertainties are demonstrated by numerical simulation.
Duc Khanh Le,Quang Khai Le,Thi Thuy Hang Tran,Duc Viet Nguyen,Thi Hang Dao,Thi Thuy Nguyen,Xuan Lam Truong,Quang Cuong Nguyen,Huy Phong Pham,Thi Thu Thuy Phan,Gajendra Babu Baktavachalam 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.2
Susceptibility of Asian corn borer (ACB), Ostrinia furnacalis (Guenée) to Bacillus thuringiensis (Bt) Cry1Ab protein was studied between 2015 and 2016 with 11 ACB populations, collected from various geographical regions in Vietnam. A concentration range of Cry1Ab from 0.20 to 26.10 ng/cm 2 of diet was evaluated against F 1 ACB neonates using diet surface-overlay bioassays. Mortality data was recorded daily until seven days after infestation. Growth inhibition was recorded at the end of seven days. The median lethal concentration (LC 50 ) varied ≈3-fold among the different populations, ranging from 0.58 to 1.83 ng/cm 2 of diet with an overall mean of 0.86 ng/cm 2 of diet. Even the lowest concentration of 0.20 ng/cm 2 caused 73.53% growth inhibition. > 90% growth inhibition was achieved at 0.82 ng/cm 2 or higher concentrations. The results reflect natural variation in Bt susceptibility among ACB populations rather than variation caused by prior exposure to selection pressures. LC 99 value (17.26 ng/cm 2 ) was generated by pooling mortality data across different populations. The upper fiducial limit of LC 99 (24.38 ng/cm 2 ) could be a potential diagnostic dose for future resistance monitoring programs. The findings from this study suggest that ACB populations in Vietnam are highly susceptible to Cry1Ab protein. This is the first report of Cry1Ab susceptibility of different ACB populations in Vietnam and will serve as a baseline for future resistance monitoring work.
Effect of tip size on adhesion and friction characteristics of patterned polymeric surface
Duc-Cuong Pham,R. Arvind Singh,Nguyen Xuan Toan,Euu-Sung Yoon 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11
Nano-pillars made of poly (methyl-methacrylate) (PMMA) were fabricated on silicon wafer by capillary force lithography technique. The pattern was investigated for its tribological properties at micro/nano-scales in comparison with flat polymeric surface. An atomic force microscope (AFM) was used to investigate adhesion and friction properties of the patterns and flat surface at nano-scale. Two AFM tips with diameter of 2.5 and 10㎛ were used to study the effect of the tip size. A reciprocating micro-tribotester using glass balls (1㎜ in diameter) as counter-body was used to study friction characteristic of the samples at micro-scale. Results indicated that the patterns exhibited significant lower nano-adhesion and micro/nano-friction when compared to those of the flat film. The reasons for the patterns to exhibit such low adhesion and friction were assigned to its reduced real contact area and increased hydrophobicity. Moreover, the adhesion and friction forces of the patterned and non-patterned surfaces increased with the AFM tip size. It was due to the increase in real contact area when the larger tip contacts with the sample surfaces.
A self-encapsulated porous Sb-C nanocomposite anode with excellent Na-ion storage performance
Pham, Xuan-Manh,Ngo, Duc Tung,Le, Hang T. T.,Didwal, Pravin N.,Verma, Rakesh,Min, Chan-Woo,Park, Choong-Nyeon,Park, Chan-Jin The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.41
<P>In this study, a self-encapsulated Sb-C nanocomposite as an anode material for sodium-ion batteries (SIBs) was successfully synthesised using an SbCl3-citrate complex precursor, followed by a drying and calcination process under an inert N2 atmosphere. When the molar ratio of SbCl3 to citric acid was varied from 1 : 1 to 1 : 4, the Sb-C nanocomposite with a molar ratio of 1 : 3 (Sb-C3) exhibited the highest specific surface area (265.97 m<SUP>2</SUP> g<SUP>−1</SUP>) and pore volume (0.158 cm<SUP>3</SUP> g<SUP>−1</SUP>). Furthermore, the Sb-C3 electrode showed a high reversible capacity of 559 mA h g<SUP>−1</SUP> at a rate of C/10 and maintained a high reversible capacity of 430 mA h g<SUP>−1</SUP> even after 195 cycles at a rate of 1C. The Sb-C3 electrode exhibited an excellent rate capability of 603, 445, and 357 mA h g<SUP>−1</SUP> at the rates of C/20, 5C, and 10C, respectively. Furthermore, a full cell composed of an Sb-C3 anode and a Na3V2(PO4)3 cathode exhibited good specific capacity and cyclability, making the Sb-C composite a promising anode material for high-performance SIBs.</P>
NGUYEN, Xuan Hung,DANG, Thuy Quynh,DINH, Thi Thao Quyen,DO, Phuong Thanh,PHAM, Thu Uyen,MAI, Duc Duong Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.6
The objective of this article is to assess the impact of corporate social responsibility (CSR) implementation on Corporate Brand Value (CBV) and Corporate Financial Performance (CFP). At the same time, the article examines the mediated role of CBV on the relationship between CSR implementation and CFP. In-depth interviews and observation techniques were used in this article on 4 experts to collect qualitative information. Quantitative analysis was based on primary data obtained from 454 employees working at enterprises providing Bancassurance services. The article uses various models of Cronbach's Alpha coefficient, Exploratory Factor Analysis (EFA), Confirmatory Factor Analysis (CFA), and Structural Equation Analysis (SEM) using SPSS 22.0 and AMOS 20.0 software. In addition, a 5-point Likert scale is used to measure observed variables. Research results show that CBV plays an intermediate role in the relationship between CSR implementation and CFP. At the same time, the implementation of CSR toward communities, customers, and workers directly impacts CBV and CFP. The article draws a new conclusion; there is no relationship found between the implementation of CSR and CFP. The result proposes implications for the state and Bancassurance service providers to develop and implement CSR-related policies and activities to enhance their brand value and financial performance.
Facile Synthesis of Si@SiC Composite as an Anode Material for Lithium-Ion Batteries
Ngo, Duc Tung,Le, Hang T. T.,Pham, Xuan-Manh,Park, Choong-Nyeon,Park, Chan-Jin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.38
<P>Here, we propose a simple method for direct synthesis of a Si@SiC composite derived from a SiO2@C precursor via a Mg thermal reduction method as an anode material for Li-ion batteries. Owing to the extremely high exothermic reaction between SiO2 and Mg, along with the presence of carbon, SiC can be spontaneously produced with the formation of Si. The synthesized Si@SiC was composed of well-mixed SiC and Si nanocrystallites. The SiC content of the Si@SiC was adjusted by tuning the carbon content of the precursor. Among the resultant Si@SiC materials, the Si@SiC-0.5 sample, which was produced from a precursor containing 4.37 wt % of carbon, exhibits excellent electrochemical characteristics, such as a high first discharge capacity of 1642 mAh g(-1) and 53.9% capacity retention following 200 cycles at a rate of 0.1C. Even at a high rate of 10C, a high reversible capacity of 454 mAh g-1 was obtained. Surprisingly, at a fixed discharge rate of C/20, the Si@SiC-0.5 electrode delivered a high capacity of 989 mAh g(-1) at a charge rate of 20C. In addition, a full cell fabricated by coupling a lithiated Si@SiC-0.5 anode and a LiCoO2 cathode exhibits excellent cyclability over 50 cycles. This outstanding electrochemical performance of Si@SiC-0.5 is attributed to the SiC phase, which acts as a buffer layer that stabilizes the nanostructure of the Si active phase and enhances the electrical conductivity of the electrode.</P>
Highly porous coral-like silicon particles synthesized by an ultra-simple thermal-reduction method
Ngo, Duc Tung,Le, Hang T. T.,Pham, Xuan-Manh,Jung, Ji-Won,Vu, Ngoc Hung,Fisher, John G.,Im, Won-Bin,Kim, Il-Doo,Park, Chan-Jin The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.6
<P>Porous Si is considered a potential anode material for next-generation Li-ion batteries (LIBs) because of its high specific capacity, low lithiation/delithiation potential, low cost, and environmental friendliness. In this work, we introduce a simplified Mg-thermal-reduction method for the production of mass-scalable coral-like bulk-Si powder with a high surface area (38 m<SUP>2</SUP> g<SUP>−1</SUP>), broad pore-size distribution (2-200 nm), and 3-dimensionally (3D) interconnected Si structure for application in LIBs. The porous, coral-like Si electrode delivered a high reversible capacity of 2451 mA h g<SUP>−1</SUP>, corresponding to ∼70% of the theoretical capacity of Si, at a rate of C/10. After 100 cycles, the porous, coral-like Si electrode maintained a capacity of 1956 mA h g<SUP>−1</SUP>, corresponding to 79.8% of the initial reversible capacity. Importantly, a reasonably high reversible capacity of 614 mA h g<SUP>−1</SUP> was achieved even at a high rate of 10C. These outstanding results demonstrate that the 3D-networked, porous, coral-like Si powder, synthesized <I>via</I> a NaCl-assisted Mg-thermal-reduction process on a stainless-steel plate over a period of one minute, can be employed as a promising anode material for the next generation of high-energy LIBs.</P>
Dual-band isotropic metamaterial absorber based on near-field interaction in the Ku band
The Linh Pham,Hong Tiep Dinh,Dinh Hai Le,Xuan Khuyen Bui,Son Tung Bui,Hong Luu Dang,Anh Duc Phan,Dac Tuyen Le,Dinh-Lam Vu 한국물리학회 2020 Current Applied Physics Vol.20 No.2
We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one diskpair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.