Catalytic Dye Oxidation over CeO2 Nanoparticles Supported on Regenerated Cellulose Membrane

A novel regenerated cellulose (RC) membrane containing cerium oxide (CeO2) nanoparticles is described in detail. In this work, CeO2 nanoparticles with high surface area and mesoporosity were prepared by a modified template-assisted precipitation method. Successful synthesis was achieved using cerium nitrate as a precursor, adjusting the final pH solution to around 11 by ammonium hydroxide and ethylene diamine, and annealing at 550 °C for 3 hours under a protective gas flow. This resulted in a surface area of 55.55 m².g–1 for the nanoparticles. The regenerated cellulose membrane containing CeO2 particles was synthesized by the novel and environmentally friendly method. The catalyst CeO2 and cellulose/CeO2 membrane were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), and Brunauer-Emmett-Teller (BET) measurements. The g-value of 2.276 has confirmed the presence of the surface superoxide species of CeO2 nanoparticles in EPR. The photocatalytic activity of the catalyst and the membrane containing the catalyst was evaluated through the degradation of methylene blue under visible light irradiation by UV-VIS measurements. The cellulose/CeO2 membrane degraded 80% of the methylene blue solution in 120 minutes, showing a better photocatalytic activity than the CeO2 catalyst, which degraded approximately 62% in the same period. It has been proven that the RC membrane is not only a good transparent supporting material but also a good adsorption for high-performance of CeO2 catalyst. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

How Foreign Ownership and Competition Affect the Credit Growth of Commercial Banks: Evidence from A Transitional Economy

This study examines the relationship between foreign ownership and market competition, proxied by bank market power, affecting the credit growth of 32 commercial banks in Vietnam from 2010 to 2020. The Random Effects Model and the Dynamic System Generalized Method of Moments were used to analyze an unbalanced panel of 278 annual observations. The findings report that foreign ownership reduces credit growth, with each percentage increase in foreign ownership reducing credit growth by 0.74%. The results indicate an inverse U-shaped relationship between competitive advantage and credit growth, with a turning point of 0.46. The main findings were found to be robust after employing an alternative market power proxy. The study recommends that bank managers and policymakers limit foreign ownership and control commercial banks’ market power to promote sustainable credit growth

Genetic diversity of two successive generations of selection in bighead catfish (Clarias macrocephalus) populations

Selective programs associated with domestication can improve fish production but also can have an impact on broodstock’s genetic diversity. In this study, the genetic diversity of original sources (G0) from wild and cultured bighead catfish populations, as well as the two successive generations (G1 and G2) subjected to selection experiments, was assessed. G0 wild adults were collected in Ca Mau conservation area and G0 cultured fish were from a hatchery in Can Tho. The G1 fish included pure crosses and crossbreeds of G0, while G2 was the offspring of the selected G1. Fin clips from 27 to 29 individuals of each fish group were randomly sampled for genetic analysis. The amplification results using six ISSR primers showed that the genetic diversity was relatively higher in G0 (effective number of alleles Ne from 1.43 to 1.49; heterozygosity He from 0.265 to 0.290) than in G1 (Ne = 1.32±0.04; He = 0.201±0.023) and G2 (Ne = 1.34±0.04; He = 0.216±0.023). Genetic differences increased between the original populations and the descending generations. To reduce the detrimental impacts of low genetic diversity in domesticated bighead catfish in the Mekong Delta, it is recommended that broodstock in later generations should be produced in a larger..

Factors Affecting Cooperation in the International Supply Chain of Seafood Enterprises: the Case of Vietnamese

Purpose: The purpose of this research is to analyze and evaluate factors affecting cooperation in the international supply chain of Vietnamese seafood enterprises.   Theoretical framework: Operations in international business context are associated with high risks, so cooperation in supply chain helps to improve management flexibility. On the other hand, acccording to the theory of resource dependency, resource sharing and information sharing strategies can affect the quality and the level of cooperation among supply chain partners.   Design/methodology/approach: To achieve the aim of this study, a literature survey related to supply chain and supply chain cooperation is carried out, and empirical analysis is conducted among 327 partners in seafood industry with the results analyzed using Cronbach’s Alpha analysis, exploratory factor analysis (EFA), and linear regression analysis (RA).   Findings: Research results have confirmed that there are six main factors directly affecting the international supply chain cooperation of Vietnamese seafood enterprises including: (1) Trust; (2) Power; (3) Distance; (4) Government policy; (5) Cooperation strategies and (6) Information sharing.   Research/Practical & Social implication: The encouraging policies and simplified export regulations are to be implemented by the government, VASEP and enterprises so the knowledge about international supply chain cooperation will be promoted with the help of comprehensive future research directions.   Originality/value: This is literally one of the first research works in Vietnam to incorporate the information sharing component into the model of affecting factors for international supply chain cooperation. Regardless of business uncertainties, the study shed new light on supply chain cooperation and promote firms to gain an edge in the global marketplace

RESEARCH ON THE MANUFACTURING MAGNESIUM FROM THANHHOA DOLOMITE BY PIDGEON PROCESS

The magnesium and magnesium alloys has applied widely in different industrial aspects in Vietnam in the modern life. Especially, the products from magnesium alloys implementing in the automotive have increased rapidly since the car elements tend to be generated by the light alloys in order to save the fuel. However, in the current time, Vietnam has no factories to produce the magnesium to adapt the domestic demand although it owns an enrich resource of raw materials. This research indicates the possibility of using the dolomite ore in Thanhhoa – Vietnam to make the magnesium as well as evaluate the primary factors like recovering temperature, reducing agent rate, recovering time having effect on the reduction efficiency of Thanhhoa dolomite by metallothermic method in vacuum (Pidgeon Process). This is basic process, low investment and suitable for the small and medium scales in Vietnam. The experiment includes heating, indicating the chemical ingredients and recovering experiment on the dolomite after calcination (dolime) by using ferrosilicon. The thermodynamic model is created to estimate the recovering efficiency in the Pidgeon. The result shows that the CaO/MgO molar ratio of calcination dolomite in Thanhhoa is nearly 1.5 which is suitable to produce magnesium in the case of highly-required efficiency and pureness. Besides, the result from the furnace of the experiment is lower than the one in the model. The samples are set up to check the influence of the rate of ferrosilicon in the compound. The result indicates that the ideal efficiency reaches 85 % with 30 % ferrosilicon. Moreover, the study confirms that the optimal operating conditions in this process are recovering during three hours at 1200 °C and 100 Pa pressure. This result proves the potential application of Thanhhoa dolomite in the industry suitable with the current condition in Vietna

Research on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy when modified by La, Ce and thermo-mechanical treatment

Influence of rare-earth (La, Ce) and thermo-mechanical treatment on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy are presented in this article. After casting, the alloy which was modified by La, Ce, the grain size of samples obtained around 40–50 µm compared to that of without about 65 µm; and after homogeneous, the grain sizes is about 30 µm. After the cold deformation process, the distance between plates is 10 µm. By EDS after casting, the samples have tended to more La, Ce elements at the grain boundary, after homogeneous, the uniformation distribution of rare-earths was presented by mapping of EDS’s results. In addition, after rolling and heat treatment, the elements were found on the grain boundary and matrix. After recrystallization annealing, the grain size is around 10 µm with the modification sample. The grain size was reduced by two processes of modification as well as thermal-mechanical treatment is a condition for increasing the ductility of the studied alloy. Further, as a result of ability deformation from the tensile test, these results demonstrate that the tensile test obtained 140 % when adding La, Ce contents into the alloy combine with thermal-mechanical treatment. The combined used of La, Ce and thermal-mechanical treatment have increased the ductility of Al-Zn-Mg-Cu allo

Reproductive Biology of Moonlight Gourami (Trichopodus microlepis) in U Minh Thuong and U Minh Ha National Parks

This study aimed to provide information about the reproductive biology of moonlight gourami (Trichopodus microlepsis) distributed in U Minh National Parks. Fish samples were collected monthly from January to October 2019 at two locations: U Minh Ha (UMH, Ca Mau, n=462) and U Minh Thuong (UMT, Kien Giang, n=635). Results showed that the maturation-stage ratios of females were similar between the two fish populations. Mature females (with stage IV-ovaries) and the increase in their gonadal somatic index (GIS) were found from June to October, indicating that this period is their spawning season. GSI reached the highest values in August with 8.04% in UMH and 6.44% in UMT. Female fish of the UMH population showed higher average fecundity (7,483±3,008 eggs/female) and larger egg diameter (762±55 µm) than those of UMT (6,898±2,952 eggs/female and 754±43 µm, respectively), but these differences were not significant (p>0.05)

Vietnam's visa policy for tourists

States employ travel visa as an instrument to leverage on visitor arrivals for various reasons. In tourism, visa plays a crucial role in facilitating potential and last-minute tourists’ decision making process. This paper focuses on the Vietnamese government’s visa policy in the context of tourism development. Adopting an economic approach, this paper reviews key achievements in tourist immigration policies and examines the challenges that deter tourists from visiting the country. This study purports that a stronger national strategy pertaining to simplification of visa processing and streamlining common visa entry union with neighboring countries within the AEC 2015 framework will translate to gains for Vietnamese tourism. __________________________________________________ Key words: economic approach, national visa policy, tourism developmen

Improving indigenous Vietnamese Black Rabbit frozen sperm quality: the role of glycine and sperm selection methods

[EN] Rabbit sperm are known to undergo damage during both cryopreservation and thawing, leading to decreased viability, motility and membrane integrity. Glycine can protect sperm and reduce damage during freezing. Swim-up is a simple semen processing method for selecting good motile sperm. The study evaluated the effect of the swim-up method and glycine with different concentrations supplemented to the frozen medium. Three indigenous black rabbits were selected for semen collection by artificial vagina. Next, semen was selected by swim-up method and diluted with glycine-added frozen medium. The samples were then transferred to 0.5 mL straws, cooled to 15°C and 5°C, placed in liquid nitrogen vapour, and finally placed directly into liquid nitrogen (-196°C). The samples were thawed and evaluated for sperm quality. The results showed that the medium supplemented with 10mM glycine in combination with swim-up method for 30 min gave the best results and was significantly different from the remaining concentrations (P<0.01), with viability rate, overall mobility and membrane integrity of 68.0%, 58.7% and 49.7%, respectively. In conclusion, 10 mM glycine concentration combined with swim-up for 30 min is the optimal choice for freezing local black rabbit semen. The study highlights the importance of optimising freezing protocols to improve the quality of frozen rabbit sperm, which can have important implications for animal breeding and conservation efforts.This study is funded in part by the Can Tho University, Code: T2022-133Tran, TTT.; Duy, NLK.; Hang, NT.; Ngoc, PK.; Tuyen, DND. (2023). Improving indigenous Vietnamese Black Rabbit frozen sperm quality: the role of glycine and sperm selection methods. World Rabbit Science. 31(4):229-236. https://doi.org/10.4995/wrs.2023.1969022923631

Super cavity model with the coupling reaction of slender body motion and water flow

 On the imperfect water entry, a high-speed slender body moving in the forward direction, rotates inside the cavity. The body's motion makes super cavity phenomena in the water flow. The water velocity and pressure fields interact during the body's motion. In this paper, the coupling simulation model is a combination of two sub-models: In the first sub-model, the motion of slender body running very fast underwater is simulated. The equation system of this sub-model is solved by Runge-Kutta method; In the second sub-model, the water flow and pressure field under reaction of very fast slender body motion are simulated by CFD model. The simulation results of this coupled model are compared with experiments based on magnitudes of velocity U by x0 direction and error percents for cavity diameter and length