Optimization of the eco-friendly synthesis of graphene oxide from graphite using Plackett–Burman and Box–Behnken models for industrial production orientation

Phuc Nguyen Thien,Giang Nguyen Thi Huong,An Vu Nguyen Thien Truong,Nam Nguyen Thanh Hoai,Anh Ly Duc,Nguyen Huynh Cam,An Hoang,Phong Mai Thanh,Hieu Nguyen Huu 한국탄소학회 2023 Carbon Letters Vol.33 No.2

In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4:Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. In addition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.

Impact of Working Capital Management on Firm's Profitability: Empirical Evidence from Vietnam

NGUYEN, Anh Huu,PHAM, Huong Thanh,NGUYEN, Hang Thu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.3

This paper investigates the impact of working capital management on the firm's profitability. The research sample includes 119 non-financial listed companies on Vietnam stock market over a period of 9 years from 2010 to 2018. Two statistical approaches include Ordinary least squares (OLS) and fixed effects model (FEM) are employed to address econometric issues and to improve the accuracy of the regression coefficients. The empirical results show the negative and significant impacts of the working capital management, which measured by cash conversion cycle (CCC) and three components of the CCC including accounts receivable turnover in days (ARD), inventory turnover in days (INVD), and accounts payable turnover in days (APD) on the firm's profitability measured by return on assets (ROA) and Tobin's Q. It implies that firms can increase profitability by keeping the optimization of the working capital management measured by the CCC, which includes shortening the time to collect money from clients, accelerating inventory flow and hold the low payment time to creditors. Besides, the profitability of firms was impacted by the sale growth rate, firm size, leverage, and age. Therefore, this paper provides a new insight to managers on how to improve the firm's profitability with working capital management.

Influence of Red Y2O3:Eu3+ Phosphor Concentration to the Multi-Chip White LEDs Color Rendering Ability

Nguyen Huu Khanh Nhan,Tran Hoang Quang Minh,Nguyen Doan Quoc Anh 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.4

In this paper, a novel solution and application of the red Y2O3:Eu3+ dopant phosphor for enhancing color rendering index to more 86 for multi-chip white LED lamps (MCW-LEDs), which have correlated color temperature (CCT) of 7700 K, 6600 K, 5600 K, are presented. Then the effect of the concentration of Y2O3:Eu3+ phosphor on the color rendering index (CRI) is simulated, analyzed and demonstrated. After that the lumen output of MCW-LEDs depended on concentration Y2O3:Eu3+ phosphor is discovered. The lumen output has a decrease tendency at large weight range due to the enhancement extinction coefficient, according to Mie-scattering theory. Simulation results provided important conclusions for selecting and developing the phosphor materials in MCW-LEDs manufacturing.

Determinants of Sustainability Disclosure: Empirical Evidence from Vietnam

NGUYEN, Anh Huu,NGUYEN, Linh Ha Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.6

The paper investigates the effect of the factors on the disclosure of sustainable development information of enterprises. The research sample includes 120 manufacturing companies listed on Vietnam stock market in 2019. This research uses ordinary least squares (OLS) to address econometric issues and to improve the accuracy of the regression coefficients. The empirical results show that five variables have a statistically significant positive effect on disclosure of sustainable development information of manufacturing companies, including firm size (SIZE), independence of board of directors (BOD), foreign ownership (FRO), return on equity (ROE), and financial leverage (LEV). The results indicate that state ownership (STO) has a statistically significant negative effect on disclosure of sustainable development information of manufacturing companies listed on Vietnam stock market. Besides, the research results also show there is a large difference in the disclosure of sustainable development information between listed companies in Vietnam, those of other emerging economies in the region, and the companies in developed markets. Therefore, this paper provides a new insight to managers and related parties on how to improve the firm's sustainability disclosure to bring benefit for the firm itself and the stakeholders by reasonable decisions about the factors that affect disclosure of sustainable development information.

Determinants of E-invoice Adoption: Empirical Evidence from Vietnam

NGUYEN, Anh Huu,NGUYEN, Thao Phuong,DANG, Giang Tra Thi Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.7

This paper aims to investigate the effect of the factors on the e-invoice at its infant stage of adoption in the context of Vietnam. Data were collected by using a questionnaire delivered to 318 participants who are managers and accountants of companies in Vietnam from June to September 2019. The statistical methods approaches are employed to address the research issues including Cronbach's Alpha testing, Explanatory Factor Analysis (EFA), and Confirmation Factor Analysis (CFA). Then, Structural Equation Modeling (SEM) is employed to assess the proposed hypotheses model of e-invoice adoption in Vietnam. The research findings showed that direct factors have a statistically significant impact on the e-invoice adoption towards behavior, and perceived behavioral control. Perceived usefulness and perceived ease-of-use positively affect attitude towards the behavior. These factors, in turn, are impacted by perceived compatibility. Based on the research results, some practicable suggestions are proposed in order to boost the number of Vietnamese enterprises voluntarily adopting e-invoice. This study indicates the important impacts of the user's attitude and perception about control ability on intention to use. In addition, some key intuitive recommendations were proposed aiming to improve the success of the e-invoice adoption of enterprises in the context of Vietnam.

Provincial Governance Quality and Earnings Management: Empirical Evidence from Vietnam

NGUYEN, Anh Huu,DUONG, Chi Thi Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.2

The paper investigates the mechanism through which corporate credit ratings affect dividend payments by decomposing the mean difference of dividends into a part that is explained by the determinants of dividends and a residual part that is contributed by the pure credit group effect, in the framework of the traditional dividend model of Fama and French (2001). Historically, better credit rated firms have shown consistently higher propensity to pay dividends especially during the economic crisis period. According to the counter-factual decomposition technique of Jann (2008), better rated firms are more responsive to the firm characteristics that have positive impact on dividends and poor rated firms are more responsive to the negative dividend predictors. As a result, good (bad) credit ratings make corporate managers become more bold (timid) in their dividend payments and they tend to pay more (less) dividends than what their firm characteristics prescribe. The degree of information asymmetry increases for the poor group firms during crisis periods and they attempt to reserve more cash in preparation for future investments. The decomposition results suggest that the credit group effect can potentially exceed the effect of firm characteristics because firms of different credit ratings can respond to the very same firm characteristics in a different manner.

CePO4:Tb Nanoparticles: Preparation, Structure and Optical Properties

Nguyen Vu Thanh,Tran Kim Anh,Nguyen Quang Liem,Nguyen Huu Quan,Nguyen The Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated. Nanocrystals of CePO4:Tb were prepared by reacting the corresponding metal chlorides, phos- phoric acid and trioctylamine at 200℃ in tris(2-ethylhexyl) phosphate (TEHP). The samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). The photoluminescence (PL) and the absorption spectra of CePO4:Tb nanoparticles will be presented. The PL spectra are described by using the well-known 5D4 - 7FJ transitions (J = 6, 5, 4, 3 ···) of Tb3+ ions with the strongest emission at 543 nm for J = 5. The dependence of PL intensity on Tb3+ concentration has been investigated.

Inhibitory Activity of Plantago major L. on Angiotensin I-converting Enzyme

Nguyen Xuan Nhiem,김영호,Bui Huu Tai,Phan Van Kiem,Chau Van Minh,Nguyen Xuan Cuong,Nguyen Huu Tung,Vu Kim Thu,Trinh Nam Trung,Hoang Le Tuan Anh,조성훈,장해동,권영인 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.3

Eight compounds were isolated from methanol extract of Plantago major L. leaves and investigated for their ability to inhibit angiotensin I-converting enzyme activity. Among them, compound 1 showed the most potent inhibition with rate of 28.06 ± 0.21% at a concentration of 100 μM. Compounds 2 and 8 exhibited weak activities. These results suggest that compound 1 might contribute to the ability of P. major to inhibit the activity of angiotensin I- converting enzyme.

Efficient Forest Fire Detection using Rule-Based Multi-color Space and Correlation Coefficient for Application in Unmanned Aerial Vehicles

Nguyen Duc Anh,Pham Van Thanh,Doan Tu Lap,Nguyen Tuan Khai,Tran Van An,Tran Duc Tan,Nguyen Huu An,Dang Nhu Dinh 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.2

Forest fires inflict great losses of human lives and serious damages to ecological systems. Hence, numerous fire detection methods have been proposed, one of which is fire detection based on sensors. However, these methods reveal several limitations when applied in large spaces like forests such as high cost, high level of false alarm, limited battery capacity, and other problems. In this research, we propose a novel forest fire detection method based on image processing and correlation coefficient. Firstly, two fire detection conditions are applied in RGB color space to distinguish between fire pixels and the background. Secondly, the image is converted from RGB to YCbCr color space with two fire detection conditions being applied in this color space. Finally, the correlation coefficient is used to distinguish between fires and objects with fire-like colors. Our proposed algorithm is tested and evaluated on eleven fire and non-fire videos collected from the internet and achieves up to 95.87% and 97.89% of F-score and accuracy respectively in performance evaluation.

Spending on Distribution Information and Communication Technologies and Cost-Effective Operation in Banks

Anh PHAN(Anh PHAN),Chi Huu LU(Chi Huu LU),Phuong Minh NGUYEN(Phuong Minh NGUYEN ) 한국유통과학회 2022 유통과학연구 Vol.20 No.9

Purpose: Many concerns have appeared in banking sector in the digital era and one of them is that technology development will increase operation costs of banks. Motivated by this issue, our study aims to explore the effect of technological and digital investments on costeffectiveness of banking operation. Research design, data and methodology: To reach a clear answer, we use the data of 12 commercial banks spanning from 2011 to 2020 in Vietnam and employ multivariate regression analysis as well as perform various robustness tests. Results: Our regression result indicates that the adverse effect of technological spending on cost-effective operation. This finding still remains unchanged when we conduct different robust tests. Also, we find that this negative impact becomes more evident in large banks than in small ones. Conclusions: The paper provides one of the most important empirical results for mangers and policy-makers in banking sphere, especially in Vietnam where regulators have been calling for continuously investing into technological innovation in banks. The evidence confirms that banks should carefully consider an increase in spending on distribution information and communication technologies when constructing business strategies related to expanding digitalization. Our research is also useful for countries having similar financial structure to Vietnam.