Journal Science and Technology Development Journal-
Published: 17 February 2019
Science and Technology Development Journal, Volume 22, pp 120-127; doi:10.32508/stdj.v22i1.1020
Abstract:Introduction: Copolymers are being used in a variety of fields because of their diversity and since any change could result in significant modifications. The butyl acrylate/methyl methacrylate copolymer is an extensively used polymer system with many advantages. This study aims to analyze some changes in copolymerization, from using different time or temperature of synthesis, in order to find an optimal process that can be applied in Vietnam. Methods: Copolymerization of butyl acrylate/methyl methacrylate copolymer with different butyl acrylate/methyl methacrylate monomer ratios was done using Xylene solvent. Copolymer compositions were determined from the Proton nuclear magnetic resonance spectra and Gel permeation chromatography. Results: The experimental results indicate that the copolymer was successfully synthesized. The highest molecular weight was 15,591 g/mol, with the lowest dispersity of 1.53 at 100 oC after 6 hours of copolymerization.
Published: 13 February 2019
Science and Technology Development Journal, Volume 16, pp 85-96; doi:10.32508/stdj.v16i4.1606
Abstract:Artificial stone is composite of unsaturated polyester and calcium carbonate that is mostly synthesized. This study aimed to investigate the effect of additives on shrinkage property of Unsaturated Polyester (UP) and mechanical properties of artificial stone such as flexural strength, impact strength, and hardness. In this paper, we tested effect of additives such as anhydride maleic (AM), acrylonitrile butadiene styrene (ABS), methyl methacrylate (MMA) and polyvinyl acetate (PVAc) with varying concentrations from 1 – 10 phr under condition process includes 2 phr BPO, 1100C cured temperature and 20 mins cured time
Published: 26 January 2019
Science and Technology Development Journal, Volume 22, pp 114-119; doi:10.32508/stdj.v22i1.1010
Abstract:Introduction: Only chemical study on the lichen Parmotrema dilatatum was found so far in the world. The lichen Parmotrema dilatatum widely distributed in Lam Dong province, Vietnam has been studied about the isolation and elucidation of several metabolites. Methods: Phytochemical study on the polar fractions of this lichen was carried out by using various chromatographic methods including thin-layer chromatography and normal phase silica gel chromatography. Results: Eight phenolic compounds were isolated. The chemical structures of isolated compounds were unambiguously elucidated by NMR spectroscopy and comparison with the data in the literature. These are 8'-O-methylsalazinic acid, salazinic acid, 8'-O-methylprotocetraric acid, diffractaic acid, lecanorin, lecanoric acid, isolecanoric acid, and diorcinolic acid. Conclusion: Among them, 8'-O-methylsalazinic acid was found as a new natural product.
Published: 14 January 2019
Science and Technology Development Journal, Volume 16, pp 57-66; doi:10.32508/stdj.v16i2.1473
Abstract:Today, enterprise resource planning system (ERP) becomes popular and it is implemented in most business (in all fields and sizes) all over the world as well as in Vietnam. However, according to consultant experts, ERP projects, though on a large scale with high cost, entail low success rate. For Vietnamese contexts, those findings above are all the more true, because most of Vietnamese enterprises are on a small scale with short-time computerization access, lack of understanding of enterprise systems, and lack of financial resources. This research focuses on exploring key factors affecting the success of ERP projects in Vietnam. Through case studies and data collection, using SPSS for data analysis, key factors affecting the success of ERP projects are listed on such a descending order as follows: Characteristics of ERP team, Quality of consultancy, Characteristics of end-users and Characteristics of business. From the abovementioned analysis, suggestions for ensuring success of ERPs in Vietnam are also proposed.
Published: 7 January 2019
Science and Technology Development Journal, Volume 22; doi:10.32508/stdj.v22i1.1009
Abstract:Introduction: Lumnitzera littorea grown at CanGio Mangrove Forest has been investigated. The present study reports the isolation, characterization and evaluation of the alpha-glucosidase inhibitory activity of isolated compounds from Lumnitzera littorea leaves. Methods: Their structures were elucidated by spectroscopic methods (including MS, 1D and 2D–NMR) and comparison with values from the literature. From the n-hexane extract, nine compounds including lupeol (1), betulin (2), betulinic acid (3), oleanolic acid (4), corosolic acid (5), -sitosterol (6), beta-sitosterol 3-O- beta-D-glucopyranoside (7), stigmast-5-ene-3beta-O-(6-O-hexadecanoyl-beta-D-glucopyranoside) (8), and stigmast-4-ene-3-one (9) were isolated and identified. Results: The results of the alpha-glucosidase inhibitory activity showed thatcorosolic acid (5) and oleanolic acid (4) were the most potent, with IC50 values of 17.86 +/- 0.42 and 18.82 +/- 0.59 ug/mL, respectively. Five of the other seven compounds exhibited inhibitory activity with IC50 values below 100 ug/mL, and higher than the positive control acarbose (127.64 +/- 0.64 ug/mL).
Published: 30 December 2018
Science and Technology Development Journal, Volume 20, pp 55-60; doi:10.32508/stdj.v20ik7.1375
Abstract:There have been various attempts to improve the surface finish after Electrical Discharge Machining (EDM) by polishing and other means. But if it is possible to improve the surface during machining it will shorten the machining time. From this viewpoint powder mixed EDM (PMEDM) is one of these processes. PMEDM not only imparts fine machined surface finish but also modifies the machined surface. However, it is necessary to understand the mechanism of PMEDM process. In this study, influence of process parameters to tool wear rate (TWR) of PMEDM using titanium (Ti) powder is presented. The objective of the study is to evaluate the main effects of workpiece material, tool material, polarity, pulse-on time, intensity of discharge, pulse-off time, and powder concentration on the TWR in PMEDM. They carried out the investigation based on the Taguchi method involving seven control factors with three levels for an orthogonal array L27 (1313).The results indicated that electrode material, electrode polarity, pulse on time, current and powder concentration were the most significant parameters that influenced the TWR. This result will be the basis for selecting the factors in further optimization studies.
Published: 4 December 2018
Science and Technology Development Journal, Volume 21, pp 98-105; doi:10.32508/stdj.v21i3.694
Abstract:In this paper, the surface of titanium dioxide (TiO2) nanotubes (NTs) was decorated with sulfur by impregnation procedure. The crystalline structure and morphology of the S-TiO2 NT hybrid catalyst were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The chemical components of S-TiO2 NT-1 sample were analyzed by energy dispersive X-ray (EDX). The results showed that sulfur impurities were incorporated into TiO2 crystal structure and decorated on its surface due to the heat treatment temperature used throughout the fabrication process. Moreover, its photocatalytic reaction was evaluated by change of adsorption intensity of methyl orange (MO) aqueous solution at wavelength of 467 nm. This work revealed that the sulfur loaded onto TiO2 NT nanostructures exhibited excellent photocatalytic efficacy for the degradation of the MO dye compared with pristine TiO2 NTs (93.12 ± 0.02% and 80.21 ± 0.04% MO degradation efficacy under UV light versus visible-light regime, respectively, after 180 minutes). This was mainly governed by sulfur ions modified on the surface of TiO2 NTs which played a critical role in promoting the separation rate of photo-induced charge carriers.
Published: 27 November 2018
Science and Technology Development Journal, Volume 20, pp 61-67; doi:10.32508/stdj.v20ik7.1212
Abstract:Banana stem from a banana farm in Duc Hoa, Long An contained 40.26% of cellulose, 15.60% of hemicellulose and 12.42% lignin. In this study, the effects of H2SO4 or NaOH concentration, temperature, time on pretreatment of banana stem were investigated. The result revealed that NaOH solution showed better effect on the pretreatment compared with H2SO4. The best pretreatment condition included NaOH concentration of 3.0%, temperature of 60 0C and time of 6 hours.
Published: 27 November 2018
Science and Technology Development Journal, Volume 20, pp 21-27; doi:10.32508/stdj.v20ik7.1207
Abstract:In this paper, we propose an effective model for aspect-based sentiment analysis. First, we combined a sentiment dictionary and syntactic dependency rules to extract reliable word pairs (sentiment — aspect). Then, thanks to ontology, we grouped those aspects and determined the sentiment polarity of each. When we conducted experiments on real reviews, the system showed positive results.
Published: 27 November 2018
Science and Technology Development Journal, Volume 20, pp 15-20; doi:10.32508/stdj.v20ik7.1206
Abstract:Demand Response program is applied in many countries as an effective instrument to regulate the electricity consumption. In this program, time of use (TOU) tariff is used widely. Optimal TOU pricing according to different objectives was mentioned in this paper such as peak load reduction, improving load curve, energy conservation, avoiding a new peak load. This is a problem with multiobjective functions in different unit of measurement and is solved by PSO algorithm. An example to find optimal TOU tariff for one utility is also presented in this paper.