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Fiscal Decentralisation and Spatial Externalities in Vietnam Provincial Economic Growth
Bui Duy Tung,Canh Phuc Nguyen,DINH THANH SU 중앙대학교 경제연구소 2021 Journal of Economic Development Vol.46 No.4
This paper aims to investigate the impacts of fiscal decentralisation on the provincial economic development in 62 Vietnamese provinces from 2011-2018. We estimate a Spatial Durbin Model (SDM) based on a growth model with spatial externalities. The focus of the paper is on the spatial spillover effects of fiscal decentralisation on the provincial income levels. The results confirm the existence of spatial interdependency among Vietnamese provinces. The findings indicate that fiscal decentralisation and physical capital not only affects the income level within one province, but also contribute positively to the outputs of nearby provinces. The study does not find significant effects of human capital on provincial income. We also show that these effects vary across five main economic regions of Vietnam. There is also evidence that the total effects are stronger in high institutional quality levels, which points out to the “sand the wheels” effect. Policy implications are also discussed.
Mathematical Modeling of a Variable Displacement Vane Pump for Engine Lubrication
Bui Ngoc Minh Truong,Dinh Quang Truong,Nguyen Thanh Trung,Ahn Kyoung Kwan 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
This paper developed a complete and accurate mathematical model for a typical variable displacement vane-type oil pump to investigate the working performance of the pump. Firstly, the detailed theoretical model was built based on pump’s geometric design and dynamic analyses. Next, numerical simulations with the constructed model and experiments on the real pump system were carried out to analyze the main power loss factors in order to develop the complete model with high accuracy. The estimated pump performance using the complete pump model was finally verified by numerical simulations in comparison with the practical tests.
Corporate Capital Structure Adjustments: Evidence from Vietnam Stock Exchange Market
Cuong Thanh NGUYEN,Cuong Manh BUI,Tuan Dinh PHAM 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.3
Building a target capital structure is one of the most important decisions in corporate financial management. The purpose of this article is to identify the determinants of capital structure and adjustment mechanism toward the target leverage. The partial adjustment model was applied on a sample of 306 non-financial companies listed on Vietnam stock exchange market during the period of 2008-2017. By the fixed effect model estimation method, the research results have discovered the factors of growth opportunities, firm size, tangible fixed assets and firm’s unique characteristics have a positive effect on the target capital structure of enterprises. Besides, profitability and dividend payment have a negative effect on the target capital structure of enterprises. Accordingly, the research results show that the average adjustment speed toward target leverage of the firms is 90.03%. Research results also demonstrate firms have higher or lower debt ratio than the target debt ratio, capital surplus or capital deficit also have an impact on the adjustment rate toward the target capital structure. The research results are consistent with the Dynamic Trade-off Theory. From this result, this article has provided policy implications for non-financial companies listed on Vietnam’s stock market in building a reasonable target capital structure according to operating timeline to maximize enterprise value.
Van-Truc Nguyen,Thanh-Binh Nguyen,Thi-Dieu-Hien Vo,Nguyen Duy Dat,Thi-Kim Quyen Vo,Xuan Cuong Nguyen,Viet-Cuong Dinh,Thi-Ngoc-Chau Le,Thi-Giang-Huong Duong,Manh-Ha Bui,Xuan-Thanh Bui 대한환경공학회 2023 Environmental Engineering Research Vol.29 No.3
This study explores the adsorption of doxycycline (DOX) from aqueous solutions onto biochar derived from banana peel, which was prepared using a potassium hydroxide activation method (KOH-BPB). The biochar properties were characterized based on morphology, surface area (SBET of 710.241 ㎡ g<SUP>−1</SUP>), functional groups, and surface charge (pHPZC = 7.7). Parameters, including initial pH, DOX concentration, and ionic strength, that influenced the DOX adsorption capacity of KOH-BPB were examined. Adsorption equilibrium of DOX on KOH-BPB was assessed through four isothermal models: the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The obtained data were most compatible with the Langmuir model (R² = 0.9879). KOH-BPB has a maximum DOX absorption capacity of 121.95 mg g<SUP>-1</SUP> which exceeds that of many comparable absorbents. The maximum DOX removal was 96.7% at pH 6, a DOX concentration of 20 mg L<SUP>-1</SUP>, and a KOH-BPB dose of 1.0g L<SUP>-1</SUP>. These findings reveal that biochar from banana peel effectively removes antibiotic residues from water. This study provides a potential, low-cost, and environmentally friendly adsorbent.
Nguyen Van Hung,Bui Thi Minh Nguyet,Nguyen Huu Nghi,Nguyen Minh Luon,Nguyen Ngoc Bich,Le Van Thanh Son,Nguyen Trung Kien,Dao Ngoc Nhiem,Nguyen Thanh Tuoi,Dinh Quang Khieu 대한환경공학회 2024 Environmental Engineering Research Vol.29 No.4
In the present work, ZnO/g-C₃N₄/biochar was prepared, and it was used for visible-light driven photocatalytic degradation of some colorants (methylene blue, rhodamine B, methyl orange) and some antibiotics (doxycycline, ciprofloxacin, amoxicilline). Biochar was prepared by pyrolysing Phragmites australis biomass. The ZnO/g-C₃N₄/biochar composite was synthesized with the alkaline hydrolysis method. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transition electron microscopy, energy dispersive X-ray/elemental mapping, ultraviolet-visible-diffuse reflectance spectroscopy, photoluminescence spectroscopy, nitrogen adsorption/desorption isotherms and X-ray photoelectron spectroscopy. The results show that ZnO nanoparticles with a large surface area are highly dispersed on the g-C₃N₄ particle surface and biochar. The composite exhibits superior photocatalytic degradation ability toward doxycycline, a broad-spectrum antibiotic of the tetracycline compared with individual components (ZnO or g-C₃N₄) and satisfies stability after six treatment cycles. The kinetics and degradation mechanisms of doxycyline were also addressed. In addition, the present catalyst also exhibits the photocatalytic degradation of methylene blue, rhodamine B, methyl orange, ciprofloxacin and amoxicillin in visible-light regions.
Nguyen Van Hung,Bui Thi Minh Nguyet,Nguyen Huu Nghi,Nguyen Mau Thanh,Nguyen Duc Vu Quyen,Vo Thang Nguyen,Dao Ngoc Nhiem,Dinh Quang Khieu 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.3
In this study, longan seeds - an agricultural by-product was used to fabricate activated carbon (LSAC) through two-step pyrolysis with pre-carbonization at low temperature in the first step and then activation by H3PO4. LSAC with large surface area and porous structure exhibits an excellent capacity of absorption towards both cationic dyes (methylene blue (MB), rhodamine-B (RhB)) and anionic dyes (methyl orange (MO), congo red (CR)). Experimental data can be described well by the pseudo-second kinetic model. The maximum adsorption capacity based on Langmuir isotherm model was found as 502.84; 397.77; 464.66 and 350.64 mg.g−1 for MB, RhB, MO and CR, respectively. The adsorption of MB, RhB and CR on LSAC is spontaneous and endothermic, while that for MO is spontaneous but exothermic. Furthermore, the adsorption mechanism of dyes on LSAC was also studied showing that it can occur by electrostatic interaction, hydrogen bonding, the filling of pores involving the interaction between dye ions with specific functional groups such as –OH, –COOH, –NH2 and –PO43− on the LSAC surface. These results suggest that LSAC material may be envisaged as a promising adsorbent for treatment of wastewater in textile industries.
Tran Cong Phong,Vo Thanh Lam,Bui Dinh Hoi 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.5
General analytic expressions for the absorption coefficient (ACF) of an intense electromagnetic wave (IEW) caused by confined electrons in doped semiconductor superlattices (DSSL) are obtained by using the quantum kinetic equation (QKE) for electrons in the case of electron-optical phonon scattering. A second-order multiphoton process is included in the result. The dependence of the ACF on the amplitude E0 and the photon energy hΩof an IEW, the plasma frequency ωp and the temperature T for a specific DSSL of n-GaAs/p-GaAs is achieved by using a numerical method. The computational results show that the dependence of ACF on the photon energy can be applied to optically detect the electric subbands in a DSSL.