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Viet Hung Pham,정진석,Thanh Truong Dang,Tran Viet Cuong,Seung Hyun Hur,Byung-Seon Kong,김의정 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.5
We report the effect of temperature on the extent of graphene oxide reduction by hydrazine and the dispersibility of the resulting chemically converted graphene (CCG) in polar organic solvents. The extent of graphene oxide reduction at high temperatures was only slightly higher than at low temperatures (30-50 oC), while the dispersibility of the resulting CCG in organic solvents decreased markedly with increasing temperature. The low dispersibility of CCGs prepared at high temperatures was greatly affected by reduction and influenced by the formation of an irreversible agglomerate of CCG at high temperatures. The reduction of graphene oxide at low temperatures is necessary to prepare highly dispersible CCG in organic solvents. CCG prepared at 30 oC is dispersible in N-methyl-2-pyrrolidone concentrations as high as 0.71 mg/mL. The free-standing paper made of this CCG possessed an electrical conductivity of more than 22,000 S/m, one of the highest values ever reported.
Pham, Viet Hung,Dang, Thanh Truong,Hur, Seung Hyun,Kim, Eui Jung,Chung, Jin Suk American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.5
<P>We report a simple, environmentally friendly approach for preparing highly conductive poly(methyl methacrylate)–reduced graphene oxide (PMMA-RGO) composites by self-assembly of positively charged PMMA latex particles and negatively charged graphene oxide sheets through electrostatic interactions, followed by hydrazine reduction. The PMMA latex was prepared by surfactant-free emulsion polymerization using a cationic free radical initiator, which created the positive charges on the surface of the PMMA particle. By mixing PMMA latex with a graphene oxide dispersion, positively charged PMMA particles easily assembled with negatively charged graphene oxide sheets through electrostatic interaction. The obtained PMMA-RGO exhibited excellent electrical properties with a percolation threshold as low as 0.16 vol % and an electrical conductivity of 64 S/m at only 2.7 vol %. Moreover, the thermomechanical properties of PMMA-RGO were also significantly improved. The storage modulus of PMMA-RGO increased by about 30% at 4.0 wt % RGO at room temperature while the glass transition temperature of PMMA-RGO increased 15 °C at only 0.5 wt % RGO.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-5/am300297j/production/images/medium/am-2012-00297j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am300297j'>ACS Electronic Supporting Info</A></P>
Influence of Corporate Governance on Dividend Policy in Vietnam
NGUYEN, Ha Viet,DANG, Hung Ngoc,DAU, Hung Hoang Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.2
The paper examines the impact of corporate governance (CG), on dividend policy (DP) of enterprises in Vietnam. The paper studies the impact of CG on DP of businesses listed on Vietnam's stock exchange in the period 2008-2018 with 2,937 observations. The data of these companies is collected from the financial statements of businesses and Vietstock data sets, as well as aggregated from the data published on some reputable securities websites. The study used GLS regression method for data collected at listed companies in Vietnam in the period of 2008-2018. The research results have found that CG, the chairman of the board of directors (BOD), and the managing director have a negative effect on the DP. Specifically, companies with strong BODs tend to pay low dividends. At the same time, research shows that factors such as profitability, financial leverage, firm size, and investment opportunities affect DP. This result underscores the importance of corporate governance (both internal and external) to the income distribution decision and provides policy implications for investors and company executives. The study finds solid evidence that alternative theory explains better the relationship between corporate governance and dividend policy. Accordingly, companies with weak corporate governance will pay more dividends.
NGUYEN, Phi-Hung,TSAI, Jung-Fa,NGUYEN, Viet-Trang,VU, Dang-Duong,DAO, Trong- Khoi Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12
This paper aims to propose a Comprehensive Decision Support Model to evaluate retail companies' financial performance traded on the Vietnam Stock Exchange Market. The financial performance has been examined in terms of the valuations ratios, profitability ratios, growth rates, liquidity ratios, efficiency ratios, and leverage ratios. The data of twelve companies from the first quarter to the fourth quarter of 2019 and the first quarter of 2020 were employed. The weights of 18 chosen financial ratios are calculated by using the Standard Deviation method (SD). Grey Relational Analysis technique was applied to obtain the final ranking of each company in each quarter. The results showed that leverage ratios have the most significant impact on the retail companies' financial performance and gives some long-term investment recommendations for stakeholders and indicated that the Taseco Air Services Joint Stock Company (AST), Mobile World Investment Corporation (MWG), and Cam Ranh International Airport Services Joint Stock Company (CIA) are three of the top efficient companies. The three of the worst companies are Viglacera Corporation (VGC), Saigon General Service Corporation (SVC), and HocMon Trade Joint Stock Company (HTC). Furthermore, this study suggests that the GRA model could be implemented effectively to ranking companies of other industries in the future research.
Structural reliability analysis using temporal deep learning-based model and importance sampling
Truong-Thang Nguyen,Viet-Hung Dang 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.3
The main idea of the framework is to seamlessly combine a reasonably accurate and fast surrogate model with the importance sampling strategy. Developing a surrogate model for predicting structures’ dynamic responses is challenging because it involves high-dimensional inputs and outputs. For this purpose, a novel surrogate model based on cutting-edge deep learning architectures specialized for capturing temporal relationships within time-series data, namely Long-Short term memory layer and Transformer layer, is designed. After being properly trained, the surrogate model could be utilized in place of the finite element method to evaluate structures’ responses without requiring any specialized software. On the other hand, the importance sampling is adopted to reduce the number of calculations required when computing the failure probability by drawing more relevant samples near critical areas. Thanks to the portability of the trained surrogate model, one can integrate the latter with the Importance sampling in a straightforward fashion, forming an efficient framework called TTIS, which represents double advantages: less number of calculations is needed, and the computational time of each calculation is significantly reduced. The proposed approach’s applicability and efficiency are demonstrated through three examples with increasing complexity, involving a 1D beam, a 2D frame, and a 3D building structure. The results show that compared to the conventional Monte Carlo simulation, the proposed method can provide highly similar reliability results with a reduction of up to four orders of magnitudes in time complexity.
Partial Feedback Linearization Control of a Three-Dimensional Overhead Crane
Le Anh Tuan,이순걸,Viet-Hung Dang,문상찬,김병수 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.4
Based on partial feedback linearization, an improved nonlinear controller is analyzed and designed for the three-dimensional motion of an overhead crane. Three control inputs composed of bridge moving, trolley travelling, and cargo hoisting forces are used to drive five state variables consisting of bridge motion, trolley movement, cargo hoisting displacement, and two cargo swing angles. The control scheme is constituted by linearly combining two components that are separately obtained from the nonlinear feedback of actuated and un-actuated states. To verify the quality of the control process, both numerical simulation and experimental study are carried out. The proposed controller asymptotically stabilizes all system states.
Some Results of Recent Investigation and Application of Rubber Blends in Vietnam
Bui Chuong,Nguyen Thanh Liem,Dang Viet Hung,Nguyen Huy Tung,Nguyen Pham Duy Linh,Nguyen Thanh Nhan,Pham Ngoc Linh,Le Anh Kien,Chu Chien Huu 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
We have investigated the change of tensile strength (TS) of Natural rubber/chloroprene rubber (NR/CR) blends during combination ageing, including heating and dynamic mechanical loading. Using model of statistical experiment, we built the equation describing the dependence of TS on four factors: temperature T, number of cyclic loadings N, contents of NR (C<sub>NR</sub>) and chloroprene (CCR). This equation allows predict the TS change of NR/CR blends after combination ageing with accepted inaccuracy – less than 10%. We also investigated the effect of nanofillers, such as nanoclay, SiO2, Fe<sub>3</sub>O4, on adhesion of some rubber blends to polyester and steel cords. It was found, in the case of EPDM/CIIR rubber blends, both nanoclay and SiO2 have no effect on adhesion to steel cords, while nano SiO2 may enhance adhesion to polyester cords. On other side, Fe<sub>3</sub>O4 may remarkably enhance adhesion of NR/CR blends to steel. Mentioned results are successfully applied in some practical rubber products working under fatigue conditions, such as rubber/steel antivibration pad for locomotive, heat resistant conveyor, water dam, underwater lift bag.
Thai Hoang,Nguyen Thuy Chinh,Nguyen Thi Thu Trang,To Thi Xuan Hang,Dinh Thi Mai Thanh,Dang Viet Hung,하창식,Maëlenn Aufray 한국고분자학회 2013 Macromolecular Research Vol.21 No.11
Ternary nanocomposites based on ethylene/vinyl acetate copolymer (EVA), maleic anhydride-grafted EVA (EVAgMA), and nanosilica were prepared in a Haake Rheomixer. The structure of the EVA/EVAgMA/silica nanocomposites was characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The blending sequence was found to have a significant effect on the microstructure of EVA/EVAgMA/silica nanocomposites and the dispersion behavior of the nanosilica in the EVA matrix. The tensile properties (tensile strength and elongation at break), thermal behavior, crystalline structure and weatherability of the nanocomposites were also studied. The results showed that the above properties of the nanocomposites were enhanced remarkably using 1 wt% EVAgMA.