Effect of synthesis temperature on the structural defects of integrated spinel-layered Li_1.2Mn_0.75Ni_0.25O_2+δ: a strategy to develop high-capacity cathode materials for Li-ion batteries

Vu, Ngoc Hung,Arunkumar, Paulraj,Im, Jong Chan,Ngo, Duc Tung,Le, Hang T. T.,Park, Chan-Jin,Im, Won Bin Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.30

<▼1><P>An integrated layered-spinel of (1 − <I>x</I>)Li1.2Mn0.6Ni0.2O2·<I>x</I>LiMn1.5Ni0.5O4 (0.15 < <I>x</I> < 0.3) was synthesized by a hydrothermal reaction followed by firing at different temperatures.</P></▼1><▼2><P>An integrated layered-spinel with a nominal composition of (1 − <I>x</I>)Li1.2Mn0.6Ni0.2O2·<I>x</I>LiMn1.5Ni0.5O4 (0.15 < <I>x</I> < 0.3) was synthesized by a hydrothermal reaction followed by firing at different temperatures. The effects of firing temperature on the phase components, cation disorder, and crystal defects, and their relationship with the electrochemical performance of the cathode material were studied. The sample fired at 650 °C showed the highest capacity of up to 320 mA h g<SUP>−1</SUP> and highest initial coulombic efficiency (98%, 2–4.9 V), but the capacity decreased dramatically to only 55% after 50 cycles. The sample fired at 850 °C showed the slowest activation of the layered phase, requiring up to several dozen cycles. The intermediate firing temperature of 750 °C showed a balance between the activation rate, capacity, initial coulombic efficiency, and cycling stability, with 270 mA h g<SUP>−1</SUP> after 10 cycles and a 99% capacity retention after 50 cycles. All samples showed different rates of the layered-to-spinel phase transformation, which depends on the activation rate. This study reports the relationships between synthesis conditions, structure, and electrochemical performance, providing a strategy to develop high-capacity cathode materials based on the (1 − <I>x</I>)Li1.2Mn0.6Ni0.2O2·<I>x</I>LiMn1.5Ni0.5O4 system.</P></▼2>

Critical Factors Affecting the Innovation Activities of Businesses: Evidence from Binh Dinh Province, Vietnam

NGUYEN, Thi Le Hang,PHAM, Ngoc Toan,DAO, Vu Phuong Linh,NGO, Thi Thanh Thuy,LE, Thi Thanh Binh Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.7

The study investigates the factors influencing the innovation activities in the enterprises in the Binh Dinh Province, Vietnam. By employing the dataset from a survey in 200 typical enterprises in Binh Dinh and using the Exploratory Factor Analysis and regression analysis, we found that there are eight factor groups affecting the innovation activities of enterprises. They include management of innovation promotion; market research capacity; leadership inspiring innovation; culture of innovation; human resources for implementing innovation; network connection; disseminating/sharing knowledge; and impact of producing/serving technology. All these factors strongly affect the innovation activities, which plays an important role in promoting the sustainable development of the Vietnamese enterprises, with the statistical significance level at 1%. Moreover, findings also show that, among these factors, the market research capacity is the strongest determinant of the innovation activity in the enterprise. An increase of 1 point of capacity of market research will increase the innovation activities in the enterprise by 0.114 point. It is followed by the management of promoting innovation, leadership inspiring innovation, and disseminating and sharing knowledge, with 0.104, 0.103 and 0.102 score, respectively. On the other hand, network connection is the weakest factor, with the score of 0.07 point.

Direct synthesis of hydrogen peroxide over palladium catalysts supported on glucose-derived amorphous carbons

Hang Thi Thuy Vu,Viet Le Nam Vo,정영민 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6

Untreated and sulfonated biomass-derived amorphous carbons were prepared by the pyrolysis of D-glucose at different temperatures, followed by sulfonation. Not only the surface functional group concentration but also the structure of polyaromatic carbon sheets was significantly affected by the carbonization temperature and sulfonation. More importantly, the carbonization temperature played a crucial role in determining the size of Pd nanoparticles (NPs) on glucose-derived carbons (GCx) and thereby affected the catalytic performance of Pd/GCx for the direct synthesis of hydrogen peroxide (DSHP). The volcano-shaped dependency between the Pd NP size and the carbonization temperature of GCx agrees well with the reverse relationship between the Pd NP size and the catalytic activity of Pd/ GCx. The flexible polyaromatic carbon sheet structure of the GCx was beneficial in increasing the sulfonic acid group content on the carbon surface and, therefore, H2O2 selectivity was improved in the presence of the Pd/S-GC2 catalyst (Pd supported on the sulfonated glucose-derived carbon pyrolyzed at 723 K). However, both H2 conversion and H2O2 productivity decreased over the same catalyst, possibly due to the decreased number of active sites on the clustered or single-site Pd. Reducing the catalyst resulted in a decrease in H2O2 selectivity by significantly lowering the Pd2+/Pd0 ratio and increasing the Pd NP size. These results clearly demonstrate that fine control of the physicochemical properties of the active metal and GCx support and their synergistic combination is essential to realize an efficient Pd catalyst supported on GCx for the DSHP reaction.

A novel strain of porcine deltacoronavirus in Vietnam

Le, Van Phan,Song, Sok,An, Byung-Hyun,Park, Gyu-Nam,Pham, Ngoc Thach,Le, Dinh Quyen,Nguyen, Van Tam,Vu, Thi Thu Hang,Kim, Ki-Sun,Choe, SeEun,An, Dong-Jun Springer-Verlag 2018 Archives of virology Vol.163 No.1

<P>Two porcine deltacoronavirus (PDCoV) strains (Binh21 and HaNoi6) were isolated from two pig farms in North Vietnam. Phylogenetic analysis of the complete genomes and the Spike and Membrane genes revealed that the two Vietnam PDCoVs belong to the same lineage as PDCoVs from Thailand and Laos; however, the N genes belonged to the same lineage as PDCoVs from the USA, Korea, China, and Hong Kong. The recombination detection program subsequently identified the major parent (S5011 strain) and minor parent (HKU15-44 strain) of the two Vietnam PDCoV strains (p < 0.01).</P>

Effect of Co-Doping and Tri-Doping with Transition Metals and a Nonmetal on Photocatalytic Activity in Visible Light of TiO2 Thin Film

Hang Nguyen Thai Phung,Van Nguyen Khanh Tran,Phuong Ai Duong,Hung Vu Tuan Le,Nguyen Duc Truong 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.11

Mono, co- and tri-doped TiO2 thin films with the transition metals (vanadium and/or chrominium) and a nonmetal (nitrogen) have been fabricated by sol-gel method. X-ray diffraction results clearly reveal anatase crystal structure for all obtained samples and doping with any dopants doesn’t change the anatase phase of TiO2. Compared to TiO2, three types of doped TiO2 thin films exhibit a red-shift in the absorption edge and have much better photocatalytic properties for methylene blue degradation in visible light region. The maximum visible-photocatalytic performance was achieved for tri-doped TiO2 sample. The mechanism for enhancing visible-photocatalytic activity of co-doped and tri-doped TiO2 thin films was also examined.

Investigation of the Ionic Conductivities of Yttria-Doped Ceria and Yttria-Stabilized Zirconia by Using the Statistical Moment Method

Le Thu Lam,Vu Van Hung,Bui Duc Tinh 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.4

The ionic conductivities of yttria-doped ceria (YDC) and yttria-stabilized zirconia (YSZ), are investigatied using statistical moment method including the anharmonicity effects of thermal lattice vibrations. The expressions for the lattice constant and the vacancy activation energy are derived in closed analytic forms in terms of the power moments of the atomic displacements. The distribution of oxygen vacancies around dopants and the important role of cation barriers on vacancy diffusion are evaluated in detail. The lattice constants, activation energies, ionic conductivities of YDC and YSZ are calculated as functions of the dopant concentration. Notably, the ionic conductivities depend linearly on dopant concentration. Our results are in good agreement with those of both previous experiments and several theoretical calculations.

Landscape Function and Tourism Industry: A Case Study of Moc Chau Plateau, Vietnam

LE, Hoa Thi Thu,TONG, Binh Thanh,VU, Ngoc Thi Minh,HO, Luu Si,PHAM, Thang Viet,TRINH, Hang Thi Thu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12

Tourism is not only a cultural service but also a resource consuming industry. Landscape function framework is a powerful tool to show the relationship between nature and people. This study collects 50 documents around the world to analyze the relationship between the 4 functional groups of the landscape (regulatory functions, production and supply functions, resident functions, information and entertainment functions) and the tourism industry. On that basis, we created an establishment for practical contact analysis of the goods and services of the landscape for tourism development in Moc Chau plateau, Vietnam. Research results show that tourism is an economic sector that benefits from the landscape and has a clear resource orientation. Moc Chau plateau has rich tourism resources and has the conditions to develop various types of tourism, especially cultural tourism based on community and resort tourism. The two cultural functions and the providing functions are the two most important functional groups for the tourism development of Moc Chau district, bringing the two most important tourism icons for Moc Chau, a green steppe, cool milk benevolent and also a district rich in national culture. From these conclusions, the authors give recommendations and notable points about landscapes in the tourism industry, especially in places with topography like Moc Chau.

Fiscal Decentralization, Corruption, and Income Inequality: Evidence from Vietnam

Hung Thanh NGUYEN,Thuy Hoang Ngoc VO,Duc Doan Minh LE,Vu Thanh NGUYEN 한국유통과학회 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.11

The objective of this research paper is to study the simultaneous relationship between fiscal decentralization, corruption, and income inequality among Vietnamese provinces. We use a balanced panel data set of 63 provinces/cities in Vietnam in the period from 2011 to 2018. The study used 3SLS-GMM (Three Stage Least Squares - Generalized Method of Moments estimator) and GMM-HAC (Generalized Method of Moments - Heteroskedastic and Autocorrelation Consistent estimator). Empirical evidence shows a strong simultaneous relationship: increased corruption will increase regional income disparities, income inequality, and increase fiscal decentralization. In addition, the results also suggest that an increase in per-capita income will reduce the level of corruption, or better control corruption of each province. The degree of increase in income inequality, which reduces fiscal decentralization, is the same for trade liberalization. All demonstrate that there is a simultaneous relationship between fiscal decentralization, corruption, and income inequality. In a region of high public governance quality, fiscal decentralization positively effects its economic growth. This issue will indirectly increase income inequality between provinces within a country. Our findings imply that a country’s fiscal decentralization strategy should be linked to improving corruption control and local governance effectiveness, indirectly improving income inequality between localities or regions.

Influence of MoS2 deposition time on the photocatalytic activity of MoS2/ V, N co-doped TiO2 heterostructure thin film in the visible light region

Hang Nguyen Thai Phung,Nguyen Duc Truong,Phuong Ai Duong,Le Vu Tuan Hung 한국물리학회 2018 Current Applied Physics Vol.18 No.6

Electron-hole separation and a narrow band-gap are essential steps to obtain efficient photocatalysis, towards which the use of co-catalysts or co-doped-TiO2 photocatalysts has become a widely used strategy. In this article, the combination of MoS2 and co-doping of V, N is the goal to achieve high performance photocatalysts. We synthesized MoS2/V, N co-doped TiO2 heterostructure thin film by solgel and chemical bath deposition methods. Herein, we investigated the influence of deposition time of MoS2 layer on visible-photocatalytic activity of the obtained samples. The thin films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UVevis spectroscopy techniques. Visible-photocatalytic activity of these samples were evaluated on the removal of methylene blue (MB) under visible light irradiation. The results show that the aforementioned heterostructure thin films have better photocatalytic activities than those of TiO2, MoS2 and V, N codoped TiO2 counterparts in visible light region. The mechanism for increasing visible-photocatalytic property of the heterostructure thin films is discussed in detail. We find that MoS2/V, N co-doped TiO2 heterostructure thin film at MoS2 deposition time of 45-min shows the highest photocatalytic performance in the visible light region with MB photodegradation rate about 99% for 150 min and the degradation rate constant is 2.06 times higher than that of V and N co-doped TiO2 counterpart.

Cloning, High-Level Expression, Purification, and Properties of a Novel Endo-β-1,4-Mannanase from Bacillus subtilis G1 in Pichia pastoris

( Vu Thi Thu Hang ),( Dinh Thi Quyen ),( Thi Tuyet Dao ),( Sy Le Thanh Nguyen ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.3

A novel gene coding for an endo-β-1,4-mannanase (manA) from Bacillus subtilis strain G1 was cloned and overexpressed in P. pastoris GS115, and the enzyme was purified and characterized. The manA gene consisted of an open reading frame of 1,092 nucleotides, encoding a 364-aa protein, with a predicted molecular mass of 41 kDa. The β-mannanase showed an identity of 90.2-92.9% (≤95%) with the corresponding amino acid sequences from B. subtilis strains deposited in GenBank. The purified β- mannanase was a monomeric protein on SDS-PAGE with a specific activity of 2,718 U/mg and identified by MALDITOF mass spectrometry. The recombinant β-mannanase had an optimum temperature of 45oC and optimum pH of 6.5. The enzyme was stable at temperatures up to 50oC (for 8 h) and in the pH range of 5-9. EDTA and most tested metal ions showed a slightly to an obviously inhibitory effect on enzyme activity, whereas metal ions (Hg2+, Pb2+, and Co2+) substantially inhibited the recombinant β-mannanase. The chemical additives including detergents (Triton X- 100, Tween 20, and SDS) and organic solvents (methanol, ethanol, n-butanol, and acetone) decreased the enzyme activity, and especially no enzyme activity was observed by addition of SDS at the concentrations of 0.25-1.0% (w/v) or n-butanol at the concentrations of 20-30% (v/v). These results suggested that the β-mannanase expressed in P. pastoris could potentially be used as an additive in the feed for monogastric animals.