Effect of electro-osmosis on lubrication of fresh cement paste-based material in contact with a metal wall

Hoang Viet Hai,Do Tu Anh,Tran Anh Tuan,Lanos Christophe,Mélinge Yannick 한국유변학회 2023 Korea-Australia rheology journal Vol.35 No.3

This paper presents an experimental investigation of the effect of electro-osmosis on lubricating the interface between the cement paste-based material and metal wall. A new experimental apparatus was developed and set up in this study. Two scales of cement paste-based materials were used and tested: cement paste and mortar. Tests performed were as follows: (i) range of potential difference varies from 5 to 30 V; (ii) range of metallic plate slope varies from 7° to 15°. The pre-movement time was reduced and the sample velocity was increased by increasing the potential difference and the slope. The rheological properties of two mixtures were determined to identify the characteristics of the fluid film at the interface that plays an important role in lubricating the sample. The permeability coefficient for managing the contact lubrication was also determined in this study.

Adaptive hierarchical sliding mode control using an artificial neural network for a ballbot system with uncertainties

Hai Le Xuan,Quoc-Dong Hoang,Soon Geul Lee,Dat Pham Xuan,Hoang Tran Viet,Minh Pham Van,Hung Pham Van,Hung Pham Viet,PHAM DUC TUAN,Duc Anh Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

Ballbots, which have been studied for over ten years, are under-actuated mobile robots that operate using the inverted pendulum paradigm. Controlling a ballbot poses a number of challenges, including maintaining the stable upright posture from the ground in all directions and making sure it follows the desired trajectory. External factors such as a minor change in contact surface properties or fabrication errors can affect the system's stabilization and transfer capabilities. In this study, an adaptive hierarchical sliding mode control algorithm based on an artificial neural network is developed to make the ballbot robust to external factors. The use of the proposed controller ensures system stability despite uncertainties including friction, accidental centrifugal forces and gravity that occur when the ballbot follows the reference trajectory. The system stability is guaranteed on the basis of Lyapunov theory. Control efficiency and robot stability under system uncertainties are demonstrated by numerical simulation.

Some characters of bacterial cellulases in goats' rumen elucidated by metagenomic DNA analysis and the role of fibronectin 3 module for endoglucanase function

Nguyen, Khanh Hoang Viet,Dao, Trong Khoa,Nguyen, Hong Duong,Nguyen, Khanh Hai,Nguyen, Thi Quy,Nguyen, Thuy Tien,Nguyen, Thi Mai Phuong,Truong, Nam Hai,Do, Thi Huyen Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.5

Objective: Fibronectin 3 (FN3) and immunoglobulin like modules (Ig) are usually collocated beside modular cellulase catalytic domains. However, very few researches have investigated the role of these modules. In a previous study, we have sequenced and analyzed bacterial metagenomic DNA in Vietnamese goats' rumen and found that cellulase-producing bacteria and cellulase families were dominant. In this study, the properties of modular cellulases and the role of a FN3 in unique endoglucanase belonging to glycosyl hydorlase (GH) family 5 were determined. Methods: Based on Pfam analysis, the cellulases sequences containing FN3, Ig modules were extracted from 297 complete open reading frames (ORFs). The alkaline, thermostability, tertiary structure of deduced enzymes were predicted by AcalPred, TBI software, Phyre2 and Swiss models. Then, whole and truncated forms of a selected gene were expressed in Escherichia coli and purified by His-tag affinity column for assessment of FN3 ability to enhance enzyme activity, solubility and conformation. Results: From 297 complete ORFs coding for cellulases, 148 sequences containing FN3, Ig were identified. Mostly FN3 appeared in 90.9% beta-glucosidases belonging to glycosyl hydrolase family 3 (GH3) and situated downstream of catalytic domains. The Ig was found upstream of 100% endoglucanase GH9. Rarely FN3 was seen to be situated downstream of X domain and upstream of catalytic domain endoglucanase GH5. Whole enzyme (called XFN3GH5 based on modular structure) and truncate forms FN3, XFN3, FN3GH5, GH5 were cloned in pET22b (+) and pET22SUMO to be expressed in single and fusion forms with a small ubiquitin-related modifier partner (S). The FN3, SFN3 increased GH5 solubility in FN3GH5, SFN3GH5. The SFN3 partly served for GH5 conformation in SFN3GH5, increased modules interaction and enzyme-soluble substrate affinity to enhance SXFN3GH5, SFN3GH5 activities in mixtures. Both SFN3 and SXFN3 did not anchor enzyme on filter paper but exfoliate and separate cellulose chains on filter paper for enzyme hydrolysis. Conclusion: Based on these findings, the presence of FN3 module in certain cellulases was confirmed and it assisted for enzyme conformation and activity in both soluble and insoluble substrate.

The Determinants of Listed Commercial Banks’ Profitability in Vietnam

Hai Thanh PHAN,Tien Ngoc HOANG,Linh Viet DINH,Dat Ngoc HOANG 한국유통과학회 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.11

The study investigates the factors affecting the profitability of listed commercial banks in Vietnam. Survey data for this research were collected from 10 Vietnamese listed commercial banks for the period from 2008 to 2018. In the study, we have built a model of econometric regression with the dependent variable being listed commercial banks’ profitability results measured through ROA. The research methods used include descriptive statistics, IV regression and OLS regression analysis, and the authors carried out the model verification with Stata 14 software. The results showed that operating efficiency, loans size, retail loans ratio, state ownership, inflation rate, and GDP growth are factors that have a positive impact on profitability On the other hand, variables such as capital size, credit risk, liquidity risk, bank size, and revenue diversification are statistically insignificant; hence, these variables are not statistically adequate to indicate the influence of those independent variables to banks’ profitability. The findings of this study suggest that the quality of assets should be considered in the context that bad debt risks come from lending heavily to the real estate sector. Meeting Basel II’s capital compliance requirements is relatively difficult for small listed commercial banks compared to bigger listed commercial banks in Vietnam.

Carbon coated MFe2O4 (M=Fe, Co, Ni) magnetite nanoparticles: A smart adsorbent for direct yellow and moderacid red dyes

Hoang Vinh Tran,Hai Van Nguyen,Doanh Viet Vu,Thu Dieu Le,Binh Thanh Nguyen,Dang Hai Le 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.2

We report here a simple approach for synthesis of carbon coated magnetite (C@MFe2O4, M=Co, Ni, Fe) with shell@core nanostructured composites that we used as magnetic-nanosorbents for direct yellow (DYG) and moderacid red (RS) as pollutant textile dyes removal via an adsorption process. The synthesized C@MFe2O4 was characterized by TEM, SEM, EDX, XRD, FT-IR and VSM techniques. TEM results indicated that C@MFe2O4 nanocomposites have 20-30 nm of MFe2O4 nanoparticle core and 2-3 nm in thickness of the amorphous carbon shell. The synthesized C@MFe2O4 nanocomposites have the zero point charge (pHZPC) at 5.5, which suggests that DYG and RS, anionic dyes can be adsorbed onto the C@MFe2O4 nanosorbents in the acidic medium. Adsorption of DYG and RS onto magnetic nanosorbents was optimized and adsorption thermodynamic parameters were evaluated, clearly indicating that the adsorption of RS onto synthesized magnetic-nanosorbents was facile more than that DYG. The adsorption isotherm data showed that the adsorption processes of DYG and RS onto Fe3O4 or C@MFe2O4 nanosorbents are more suitable for the Langmuir model than Freundlich model. The maximum adsorption capacity (qmax) of DYG dye onto Fe3O4, C@Fe3O4 and C@CoFe2O4 adsorbents was 14.641, 36.232 and 7.85mg g1, respectively; meanwhile, these values were 41.152, 61.728 and 39.683mg g1 for RS dye. These obtained data indicate that the developed Fe3O4, C@Fe3O4 and C@CoFe2O4 nanoparticles can be used as recoverable and recyclable adsorbents for not only organic pigments adsorption but also for heavy metal ion removal or protein extraction as well.

Outcomes of liver transplantation for hepatocellular carcinoma: Experiences from a Vietnamese center

Khai Viet Ninh,Dang Hai Do,Trung Duc Nguyen,Phuong Ha Tran,Tuan Hoang,Dung Thanh Le,Nghia Quang Nguyen 한국간담췌외과학회 2024 Annals of hepato-biliary-pancreatic surgery Vol.28 No.1

Backgrounds/Aims: Liver transplantation (LT) provides a favorable outcome for patients with hepatocellular carcinoma (HCC) and was launched in Vietnam in 2004. In this study, we evaluated the short-term and long-term outcomes of LT and its risk factors. Methods: This retrospective study analyzed HCC patients who underwent LT at Viet Duc University hospital, Vietnam, from 01/2012–03/2022. The following data were gathered: demographics, virus infection, tumor characteristics, alpha-fetoprotein (AFP) level, Child-Pugh and MELD scores, selection criteria, type of LT, complications, 30-day mortality, and disease-free and overall survival (DFS and OS). Results: Fifty four patients were included, the mean age was 55.39 ± 8.46 years. Nearly 90% had hepatitis B virus-related HCC. The median (interquartile range) AFP level was 16.2 (88.7) ng/mL. The average MELD score was 10.57 ± 5.95; the rate of Child-Pugh A and B were 70.4% and 18.5%, respectively. Nearly 40% of the patients were within Milan criteria, brain-dead donor was 83.3%. Hepatic and portal vein thrombosis occurred in 0% and 1.9%, respectively; hepatic artery thrombosis 1.9%, biliary leakage 5.6%, and postoperative hemorrhage 3.7%. Ninety-day mortality was 5.6%. Five-year DFS and OS were 79.3% and 81.4%, respectively. MELD score and Child- Pugh score were predictive factors for DFS and OS (p < 0.05). In multivariate analysis, Child-Pugh score was the only significant factor (p < 0.05). Conclusions: In Vietnam, LT is an effective therapy for HCC with an acceptable complication rate, mortality rate, and good survival outcomes, and should be further encouraged.

Effect of post-synthesis annealing on properties of SnS nanospheres and its solar cell performance

트롱윈탐윈,Ha Hai Thi Hoang,Thanh Kieu Trinh,Viet Thanh Hau Pham,Ryan Patrick Smith,박진호 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4

SnS nanospheres (NSPs) were synthesized, and the effects of thermal annealing on the structural, morphological, chemical compositional and optical properties were examined. As-synthesized SnS NPSs with a mean size of 3- 4 nm underwent a solid state morphological transformation by high temperature annealing in a nitrogen environment. Upon annealing, the size of SnS NSP increased to 5-6 nm with enhanced crystallinity. Also, the photoluminescence (PL) of the nitrogen-annealed samples slightly decreased in intensity with accompanying red-shift in spectrum. The power conversion efficiency of the solar cells using a polymer and the SnS NSPs was ~0.71%. These results confirm that the SnS NSPs demonstrate a potential as an inorganic material to be used in organic-inorganic hybrid bulk heterojunction (BHJ) photovoltaic devices.

New Cytotoxic Benzopyrans from the Leaves of Mallotus apelta

Phan Van Kiem,Nguyen Hai Dang,Ha Viet Bao,Hoang Thanh Huong,Chau Van Minh,Le Mai Huong,이정준,김영호 대한약학회 2005 Archives of Pharmacal Research Vol.28 No.10

Two new benzopyrans 6-[1'-oxo-3'(R)-hydroxy-butyl]-5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran (1) and 6-[1'-oxo-3'(R)-methoxy-butyl]-5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran (2) were isolated from the leaves of Mallotus apelta Muell.-Arg., (Euphorbiaceae). Their chemical structures were elucidated by spectroscopic analyses, especially by 1D-, 2D-NMR and MS spectra. Compound 1 was found to have strong cytotoxic effect against two human cancer cell lines as human hepatocellular carcinoma (Hep-2, IC50: 0.49 µg/mL) and rhabdosarcoma (RD, IC50: 0.54 µg/mL), while compound 2 showed moderate activity against Hep-2 cell line (IC50, 4.22 µg/mL) by in vitro assay.

Equivalent Convective Heat Transfer Coefficient for Boundary Conditions in Temperature Prediction of Early-Age Concrete Elements Using FD and PSO

Long Nguyen-Ngoc,Tu Anh Do,Viet Hai Hoang,Tuyet Thi Hoang,Tam Duc Tran 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

Engineering infrastructure includes a large number of concrete structures. The main binder used in concrete is Portland cement, which reacts with water when mixing. During the chemical reaction (cement hydration) heat is released causing non-uniform temperature distribution and subsequent internal stresses that may crack the concrete. Therefore, accurate prediction of concrete temperature evolution in design and control of concrete temperature in construction are crucial tasks for engineers. This paper presents the development of a finite difference (FD) model for predicting thermal behavior of concrete structures during cement hydration. A formwork or insulation layer that covers the outer of the concrete was accounted for in the model. The temperature profiles calculated by the proposed model show close agreement with those measured from a concrete bridge footing and a concrete cube. The Particle Swarm Optimization (PSO) algorithm was adopted to compute an “equivalent convection coefficient” for the convection boundary condition in the simplified model for several common insulation materials. The results show that using the simplified model along with an equivalent convection coefficient can give a significant reduction in the computation time while the accuracy is still maintained. In addition, an equation for estimating an equivalent convection coefficient for a given insulation material was developed for design and practical purposes. The proposed method can be used in the design of concrete structures and control of concrete temperature to prevent early-age thermal cracking thus ensuring the expected durability and service life. From the obtained results, varying equivalent convection values are also recommended to be used for different insulation materials.

New Cytotoxic Benzopyrans from the Leaves of Mallotus apelta

Kiem Phan Van,Dang Nguyen Hai,Bao Ha Viet,Huong Hoang Thanh,Minh Chau Van,Huong Le Mai,Lee Jung Joon,Kim Young Ho The Pharmaceutical Society of Korea 2005 Archives of Pharmacal Research Vol.28 No.10

Two new benzopyrans 6-[1'-oxo-3'(R)-hydroxy-butyl]-5,7 -dimethoxy-2,2-dimethyl-2H-1-ben-zopyran (1) and 6-[1'-oxo-3'(R)-methoxy-butyl]-5,7 -dimethoxy-2,2-dimethyl-2H-1-benzopyran (2) were isolated from the leaves of Mallotus apelta Muell.-Arg., (Euphorbiaceae). Their chemical structures were elucidated by spectroscopic analyses, especially by 1D-, 2D-NMR and MS spectra. Compound 1 was found to have strong cytotoxic effect against two human cancer cell lines as human hepatocellular carcinoma (Hep-2, $IC_{50}\;:\;0.49\;{\mu}g/mL$) and rhabdosarcoma (RD, $IC_{50}\;:\;0.54\;{\mu}g/mL$), while compound 2 showed moderate activity against Hep-2 cell line ($IC_{50}\;:\;4.22\;{\mu}g/mL$) by in vitro assay.