• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2647-2662
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• 2014

This paper proposes an efficient and low complexity power-loading algorithm for MIMO-OFDM downlink based cognitive radio system that maximizes the sum rate of single secondary user (SU) under constraints on the tolerable interference thresholds between secondary user and primary user's frequency bands and the total transmission power. Our suboptimal algorithm is based on the $2^{nd}$ order interference tracking and nulling mechanism to allocate transmission power of the subcarriers among SU's scheme. The performance of our proposed suboptimal scheme is compared with the performance of the classical power loading algorithms, e.g., water filling, $1^{st}$ order interference tracking, nulling, and other suboptimal schemes. Numerical results show that our algorithm has low complexity but obtains a higher channel capacity than that of some previous suboptimal algorithms in some scenarios. We dedicate also that for a given interference threshold, the $2^{nd}$ order interference tracking mechanism has dynamic number of nulling position instead fixed number of nulling position.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2645-2648
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• 2014

In this paper ultrafine copper nanoparticles (CuNPs) were prepared from copper salt via chemical reduction method with sodium citrate dispersant and polyvinylalcol (PVA) capping polymer. The colloidal CuNPs were characterized by using UV-Visible spectroscopy, Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) techniques. Our obtained results indicated that the CuNPs were produced ranging from 2 to 4 nm in diameter. The colloidal solution at 7 ppm of CuNPs exhibited a powerful antifungal activity against Corticium salmonicolor (C. Salmonicolor). Fungal killing assays showed colloid solutions containing 10 ppm of CuNPs killed entirely the cultured fungus. A highly killing activity against the fungus was also performed when the CuNPs were sprayed on pink disease-infected rubber trees. These positive results may offer a great potential to produce CuNPs-based eco-fungicide for pink disease.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.3
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• pp.205-214
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• 2019

This paper aims to discover factors and their influences degree to repurchase organic cosmetic in Vietnam. In addition, this research also discloses the main segments that have high demand re-buying intention based on demographic groups of gender, age, income, educational level, job, type of products, and place of production. Twenty-eight scale was designed based on previous studies and adjusted to match the 5-point Likert scale to conduct measurement. By using survey method to test hypotheses and set up conceptual models to collect 295 Vietnamese consumers who have experience in consuming organic cosmetic by explain the results through Smart PLS software. The findings show that there is positive attitude of customers to the intention of acquiring organic cosmetics, green perceived and customer satisfaction. In addition, customer satisfaction, knowledge of products, safety values, and environmental protection consciousness also play important roles to form a positive attitude of customers for products. Moreover, the consciousness of green living of consumers accounts for a high proportion in creating customer satisfaction for organic products. The results show useful information for current premises to determine the factors that influence the decision to repurchase organic cosmetic product, that provide business strategies.

• Journal of Information Technology Applications and Management
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• v.27 no.1
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• pp.147-171
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• 2020

In-app advertisement is a fast-growing trend in mobile advertising, where user acceptance of ads is facilitated by the fact that users have voluntarily downloaded the app through which the ad is served. However, research in this ad category is limited. This study applies an extended version of the theory of planned behavior. Analysis results from 412 young mobile users in Vietnam using structural equation modeling showed that while localization and perceived enjoyment affected user intention to watch in-app ads as expected, perceived behavioral control and trust did not. Such results may be due to embedding the ads to applications, confusing users' behavioral intentions. The results underline the need for more future research in the area. In practical terms, companies should improve localization and entertainment aspects of ads to create more relevant and engaging advertisements.

• Natural Product Sciences
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• v.12 no.1
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• pp.29-37
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• 2006

One hundred and twenty six Vietnamese traditional herbals belonging to 59 families were screened for their free radical (DPPH) scavenging activity and inhibitory effect on lipid peroxidation. Of these, MeOH extracts of seven plants, including Euphorbia thymifolia (leaf), Gnetum montanum (stem), Heterosmilax erythrantha (root), Morus alba (leaf), Syzygium formosum (leaf), Jussiaea repens (aerial parts), and Camellia sinensis (leaf), exhibited significant antioxidant activities. All of these herbs showed remarkable free radical scavenging activities with $IC_{50}$ values of 11.0, 14.5, 17.0, 13.6, 10.8, 7.7, and $8.5\;{\mu}g/ml$, respectively, and significant inhibitory effects on lipid peroxidation with 79.7, 83.8, 78.9, 82.5, 88.8, 88.0, and 96.2% inhibitions, respectively, at the concentration of $50\;{\mu}g/ml$.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.168-169
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• 2011

The aim of this paper is to present a new algorithm for the load flow problem using modified Newton-Raphson (NR) iteration method and a approach to derive a simple formula to compensate the reactive power at some heavy load bus. The reactive power source used in this research is the DG which is adjacent to the heavy load. Phenomena of low voltages may cause the load flow calculation process to diverge. In modified NR method, low voltages will be detected and corrected before the next iteration. Therefore, the results of load flow calculation process satisfy the voltage constraint i.e. higher than the lower voltage limit or higher than the critical voltage in case the conventional load flow diverges. Linearizing the power network using PTDFs is a simple method with accepted errors. A new value of voltage at the DG terminal is computed in terms of the voltage deviation of load buses. In this approach, solving the entire system is unnecessary.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.3
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• pp.53-62
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• 2020

The study aims to provide some plausible explanation for why Vietnamese listed companies only stop at the level of truthful presentation of information related to accounting data through the opinion of independent auditors. The information is only at the level of compliance with the requirements of Circular 155/2015/TT-BTC in form, but in essence is sketchy. What factors affect the level of voluntary disclosure of listed companies in Vietnam? In order to identify the factors affecting voluntary information disclosure on annual reports of listed companies, the study collected data on annual reports of 122 companies listed on the stock market in Ho Chi Minh City in the period 2015-2018 and uses regression analysis methods. The research presents 8 factors affecting the level of voluntary information disclosure including: Firm size, Listed time, Profitability, Solvency, Separation of board of directors and executive director, Board size, Organizational ownership and Foreign ownership. Next, the study conducted descriptive statistical analysis correlation coefficient analysis to examine the correlation and relevance of independent variables measured by the scale ratio, testing multiple linear regression model. The results of the study show that factors listed time, profitability and organizational ownership affecting voluntary information disclosure on annual reports of listed companies in Vietnam.

• Journal of Distribution Science
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• v.18 no.6
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• pp.83-91
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• 2020

Purpose: Research on the behavior of using digital banking services plays an important role for banks in the context of increasingly competitive banks, not only for domestic banks but also for foreign banks. Along with the development of science and technology brings new approaches to banking industry, digital banking increases the effectiveness of banking activities. Besides, information safety brings different feeling about digital banking system. Therefore, this research evaluates the relationship between Information safety and Intention to use banking services in Vietnam. Research design, data and methodology: With 329 Vietnamese customers using digital banking, reliability test, and structural equation model (SEM) analysis method. Results: the research shows that information safety has directly effects on perceived ease of use (PU), perceived risk (RIS) of customers to digital banking services. Perceived trust (TRU) has a negative impact on RIS. Perceived of usefulness (PEU) has a positive impact on attitude towards service (ATT), and RIS has a negative impact on ATT. RIS, PEU, ATT, convenience and enterprise image have positive effects on intention to use digital banking service. Conclusions: From the research results, the authors also propose some recommendations to enhance the intention to use digital banking services in Vietnam.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.1
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• pp.153-158
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• 2020

The study aims to identify the factors affecting employee loyalty in the case of small and medium enterprises (SMEs) in Tra Vinh province, Viet Nam and to find out critical factors affecting the loyalty of employees in SMEs. This is implemented with the method of collecting primary data of 320 employees working at SMEs in 5 districts including: Cau Ngang, Tra Cu, Chau Thanh, Cang Long, Tieu Can) and Tra Vinh City, Viet Nam. Using the multivariate regression method, the researchers have found 6 factors affecting employee loyalty: colleagues, leaders, job characteristics, remuneration policies, organizational culture, and working environment. Particularly, learning opportunities may not be not statistically significant for employees' loyalty towards small and medium-sized enterprises in Tra Vinh province. From the above research results, the authors have proposed implicational piolicies such as: focusing on colleague relationships, improving leadership of business owners, attaching importance to appropriate work arrangement, having appropriate remuneration policies for laborers, building effective organizational culture and working environment to improve employee loyalty at SMEs. From the above policy implications, helping business owners realize the aspirations of workers in small and medium-sized enterprises more closely in the future, in order to sustainably develop the business system in Vietnam.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1794-1798
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• 2014

Graphitic g-$C_3N_4-WO_3$ composite was synthesized simply by decomposing melamine in the presence of $WO_3$ at $500^{\circ}C$. The obtained material was characterized by XRD, SEM, IR and XPS. The results showed that the as-prepared composite exhibits orthorhombic $WO_3$ phase coated by g-$C_3N_4$ and the g-$C_3N_4$ decomposed completely with N-doped $WO_3$ remaining at elevated calcination temperatures. The photocatalytic activity of the composite was evaluated by the photodegradation of methylene blue under visible light. An enhancement in photocatalytic activity for the graphitic g-$C_3N_4-WO_3$ composite compared to the conventional nitrogen-doped $WO_3$ was observed, which can be attributed to the presence of g-$C_3N_4$ in the material.