Vietnam Journal of Science, Technology and Engineering

3-6

Authors: Tran Duc Dai, Dao Duc Thien, Nguyen Thanh Tam*

Four flavone glycosides including apigenin 7-O-β-glucoside (1), chrysoeriol 7-O-β-glucoside (2), rhoifolin (3), and 3′-methoxyapiin(4) were isolated from the n-butanol extract of the whole plant Uraria crinita collected in the phu Tho province, Vietnam. Their structures were elucidated by 1D- and 2D-NMR spectra and compared with those reported in the literature. Compounds 1-3 were obtained from the genus Uraria for the first time

13-19

Authors: Mai Thi Tuyet Phan*, Boi Van Luu, Lan Ngoc Pham

The maleic anhydride-α-tetradecene copolymer (OMAC) with an approximate relative maleic anhydride to α-tetradecene composition ratio of 1:1.2 was synthesized by free radical copolymerization. The copolymers were modified by the esterification reaction between the anhydride groups and the OH- group of hexadecanol. Comb-type (-maleic acid cetyl ester-co-α-tetradecene-) copolymers (MCEC) with various ratios of alkyl group/carboxyl group (r) were investigated. Upon cooling, the MCEC changed the crystallization state of the wax crystals, and reduced the pour point of the biodiesel, which was observed by pour point and dynamic viscosity testing. The MCEC efficiency that improved the cold flow properties of the biodiesel was found to be correlated to r. MCEC with r=2.76 was found to be the most effective in improving the flow ability of the palm oil biodiesel. Our study demonstrates the ability of MCEC3 at 1000 ppm concentration to reduce the pour point of palm oil biodiesel to 10.5oC and the dynamic viscosity up to 1.04 mPa.s. A correlation was found between the number and the length of the pendant alkyl groups of additives and the compositions of the fatty acid methyl ester of the biodiesel.

25-31

Authors: Trung-Kien Hoang*, L. Vido, Dinh-Quang Nguyen

This article proposes an easy-to-use approximation for air-gap permeance calculations in a reluctance network. An extension of the overlap area between the stator and its corresponding rotor tooth to a position where the permeance becomes zero is also proposed. The advantage of this method is the simplification of conventional complex reluctance calculations while maintaining high accuracy. The proposed approach is applied to a double excitation synchronous motor, which usually requires a 3D simulation tool for the calculations. The validation of the accuracy of the proposed method on the flux linkage, back EMF, and electromagnetic torque are accomplished by comparison with those obtained from a conventional method and experimental data. The results of the comparison recommend the use of the proposed method for different electrical motor geometries.

39-44

Authors: Manh-Hung Ha*, Hoang-Anh pham

Direct design using nonlinear inelastic analysis has been recently enabled for structural design as this approach can directly predict the behaviour of a structure as a whole, which eliminates capacity checks for individual structural members. However, the use of direct design is often accompanied by excessive computational efforts, especially for complicated structural design problems such as optimization or reliability analysis. In this study, we introduce an efficient method for the sizing optimization of truss structures employing nonlinear inelastic analysis for the direct design of structures. The objective function is the total weight of the structure while the strength and serviceability constraints are evaluated with nonlinear inelastic analysis. To save computational cost, an improved differential evolution (DE) algorithm is employed. Compared to the conventional DE algorithm, the proposed method has two major improvements: (1) a self-adaptive mutation strategy based on the p-best method to enhance the balance between global and local searches and (2) use of the multi-comparison technique (MCT) to reduce redundant structural analyses. The numerical results of a 72-bar truss case study demonstrate that the performance of the proposed method has significant advantages over the traditional DE method.

52-57

Authors: Truong Ngoc Quynh phuong, pham Van Hung, Nguyen Thi Lan Phi

The objectives of this study were to optimize the extraction conditions of flavonoids from the pomelo peel using the Box-Behnken response surface methodology and to investigate the chemical composition and biological activities of the extracts from three different pomelo species under optimized extraction conditions. Three extraction condition factors of were varied, including the solid-solvent ratio (1/15-1/45 g/ml), temperature (30-60oC), and time (20-60 min), which affected the efficiency of the total flavonoid content (TFC). The high R2 coefficient of 0.93 indicated that the experimental data obtained in this study fit well to a second-order polynomial using multiple regression analysis. The maximum TFC extracted from the pomelo peel was 6.0 mg/g (dried basis, db), which was obtained using Derringer’s desired function methodology under the following optimum conditions: a solid-solvent ratio of 1/44 g/ml, temperature of 30.7oC, and time of 34.6 min. The results also indicated that the Tan Trieu pomelo peel had the highest TFC and naringin concentration followed by the Nam Roi and Duong Hong pomelo peels, whereas the Nam Roi pomelo peel had a higher hesperidin concentration than the others. The extracts of the pomelo peels exhibited strong antioxidant activities with low IC50 values. However, these extracts showed only a slight effect on cancer cells, including lung cancer and breast cancer, when tested at 100 μg/ml

64-69

Authors: Nguyen Thi Thanh Loan, Le Thi Xoan*, Pham Thi Nguyet Hang, Nguyen Van Tai

We previously demonstrated that Panax notoginseng (pNG) root extract treatments exertedneuroprotective effects on brain injuries using middle cerebral artery occlusion in mice. The present study aims to investigate the neuroprotective effects of PNG extract and its ginsenosides Rg1 and Rb1 on ischemic neuronal damage caused by oxygen and glucose deprivation (OGD) in mouse organotypic hippocampal slice cultures (OHSCs). Before the experiments, hippocampal slices collected from 7-day-old Swiss mice were cultured for 7 days. OGD was triggered in OHSCs for 30, 60, or 90 min with the aim of finding the optimal period of OGD for drug testing. PNG extract (10, 30 μg/ml), ginsenosides Rg1 and Rb1 (5, 25 μM), or MK-801 25 μM, a reference drug, was added to the culture medium 24 h before OGD and these treatments were continued for 24 h after the optimum 60-min period of OGD. After 24 h of OGD exposure, the measurement of propidium iodide uptake was analysed in OHSCs to evaluate neuronal cell damage. The results showed that OGD time-dependently increased PI uptake of the OHSCs. PNG 30 μg/ml treatment reduced the OGD-induced neuronal cell damage in OHSCs. Ginsenosides Rg1 25 μM, Rb1 (5, 25 μM), as well as MK-801 (25 μM) significantly inhibited PI uptake 24 h after OGD exposure. However, ginsenoside Rg1 5 μM did not show any significant effects on the OGD-induced neuronal cell damage. These findings indicated that ginsenosides Rg1 and Rb1 contributed to the neuroprotective effects of PNG against ischemic damage in OHSCs and the neuroprotective effect of ginsenoside Rb1 was stronger than that of ginsenoside Rg1.

74-80

Authors: The Duc Ngo

Glyphosate has become the most widely used herbicide worldwide since 1974 with a global use of 8.6 billion kg (glyphosate active ingredient) between 1974 and 2014. This study reports on glyphosate resistant (GR) weeds and their resistance mechanisms based on global scientifically reported cases. Forty-nine different weed species have evolved resistance to glyphosate in 29 countries with a total of 318 identified cases worldwide. Fifty percent of these resistance cases were found in glyphosate-resistant cropping systems. There were 255 identified cases (80.2%) of glyphosate resistance in the top five countries (in terms of number of cases and species), namely USA, Australia, Argentina, Brazil, and Canada. The five most popular weed species (in terms of number of cases) found to be resistant to glyphosate were Conyza canadensis, Amaranthus palmeri, Amaranthus tuberculatus, Lolium perenne ssp. Multiflorum,and Ambrosia artemisiifolia with 42, 42, 29, 26, and 21 reported cases, respectively. Out of 49 weed species, 19 GR weed species were found to not only be resistant to glyphosate but also to other herbicide sites of action (multiple herbicide resistance). Glyphosate resistance mechanisms in weeds include (1) target-site alterations: target-site mutation and target-site gene amplification; and (2) non-target-site mechanisms involving different modes of exclusion from the target site: reduced glyphosate uptake, reduced glyphosate translocation, and enhanced glyphosate metabolism. It is essential to have an integrated weed management program that includes not only smart herbicide mixtures and rotations, but also cultural, manual, mechanical, and crop-based weed management methods.

89-96

Authors: Thi Yen Ta*, Thi Anh Tuyet Nguyen, Hoang Thi Hong Van

The plastic industry is an economic sector that plays an important role in promoting a circular economy in Vietnam. This study used the updated 2018 input-output (IO) table to identify and analyse the production and consumption of seven different plastics including: HDPE, PS, PE, PET, PVC, PP, and others. The study also integrated the IO model to unveil the environmental burden of these plastics through the plastic demand of 40 economic sectors and households. As a result, in 2018, the amount of direct solid waste from the plastic industry was 58,147 tons and the amount of indirect solid waste from the plastic industry to other economic sectors and the household sector were 214,258 tons and 6,262 tons, respectively. Agriculture and its services, food processing, fashion manufacturing, basic chemical production, electrical and electronic equipment production, and transport production embodied the highest indirect burdens due to their use of plastic products. This study contributes to MFA research and developing strategies for sustainable production and consumption of plastics and the management of plastic waste in Vietnam.