https://jst.vn/index.php/old Journal of Science & Technology en-US Old Journal 2354-1083 https://jst.vn/index.php/old/article/view/563 In this study, rGO/WO₃ nanocomposites were synthesized by one-pot hydrothermal method for photocatalytic applications. Properties of the synthesized materials were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), UV–Vis absorption spectroscopy and Fourier-transform infrared spectroscopy (FTIR). XRD analysis documented the formation of the hexagonal phase WO₃ with high crystalline quality. SEM images revealed that the WO₃ nanorods and layered rGO materials were synthesized. The band gap of the rGO/WO₃ composite calculated from the UV–Vis spectra is about 2.7 eV which is smaller compared to that of bare WO₃ (3.1 eV). Photocatalytic results under UV light irradiation showed that the rGO/WO₃ nanocomposite exhibited significantly higher photocatalytic activity than WO₃, where the rGO/WO₃ and WO₃ degraded about 80% and 55% of methylene blue within 100 min under UV irradiation, respectively. Quang Dat Do Van Nang Lam Thi Lan Phuong Vo Thi Lan Phuong Nguyen Thi Ngoc Ha Hoang Duc Hoa Nguyen Copyright (c) 2020 Old Journal 140 36 39 https://jst.vn/index.php/old/article/view/564 In this study, Fe₂O₃ nanopowder was synthesized by sol-gel method from the raw materials Fe(NO₃)₃.9H₂O and oxalic acid C₂H₂O₄.2H₂O to find the suitable materials applying for rechargeable Fe-air battery anode. The structure, size and morphology of the obtained Fe₂O₃ materials were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical properties of Fe₂O₃ materials have been investigated via cyclic voltammetry measurement. The effect of carbon additive (AB) in Fe₂O₃/AB electrodes was also investigated to evaluate its applicability in the rechargeable Fe-air battery. The results showed that the fabricated Fe₂O₃ materials had clear redox peaks, especially Fe₂O₃/AB electrode provided high redox current suggesting that its cyclability was better when AB was added in the electrode. The additive AB increased the electrical conductivity of the electrode and improved the cyclability of the Fe₂O₃/AB electrode. Beside that, K₂S additive in electrolyte facilitated the redox reaction rate of iron, reduced hydrogen evolution, leading to increased redox current, and thus improved the capacity and cycling efficiency of Fe₂O₃/AB electrode. Thi Hang Bui Copyright (c) 2020 Old Journal 140 40 44 https://jst.vn/index.php/old/article/view/566 Kinetics of the reactions between propargyl radicals with water molecule and hydroxyl radical were investigated by TST, VST and RRKM theories on the basis of the mechanisms of both reactions researched by means of density functional theory (DFT). The calculated results show that the C₃H₃ + H₂O reaction is unlikely to occur at room temperature (k = 4,10x10⁻³⁴ cm³ molecule⁻¹ s⁻¹ at 300 K, 1atm), while the C₃H₃ + OH system reacts very fast with a rate constant k(T) = 1,39x10⁻¹¹T⁰.³⁵exp(-26,42/T) cm³ molecule⁻¹ s⁻¹ depending on the temperature in the range 300-2100 K. In addition, the results of the second reaction are in good agreement with the experimental results of Hansen and Miller (500-2100 K) and Eiteneer, B. and Frenklach (1100-2100 K). Van Tien Pham Ngoc Tue Nguyen Copyright (c) 2020 Old Journal 140 50 55 https://jst.vn/index.php/old/article/view/567 In this study, porous scaffolds were fabricated using inorganic material-hydroxyapatite and chitosan for bone-tissue engineering. The combination of hydroxyapatite and chitosan may result in increasing biocompatibility of the scaffolds. The scaffolds were prepared by solvent casting and paticulate leaching method. Bioactivity of the scaffolds was evaluated through in vitro experiments by soaking scaffold samples in simulated body fluid (SBF). The scaffolds obtained were highly porous and interconnected with a mean pore size of around 200 µm and porosity about 79 %. The apatite-mineral layer was produced on the HAp/chitosan after 10 days of soaking in SBF, however, it was not observed on the chitosan scaffold after 10 days soaking. The results revealed that the HAp/chitosan scaffold showed better bioactivity than the chitosan scaffold. Thanh Hoai Tran Kim Nga Nguyen Copyright (c) 2020 Old Journal 140 56 60 https://jst.vn/index.php/old/article/view/568 Mango (Mangifera indica L.) belongs to the family of anacardiaceae, which is a popular tropical plant distributed in Vietnam. Mangiferin (1) was isolated from the leaves of Mangifera indica L. by reflux extraction and ultrasound-assisted extraction methods. Chemical structure of compound 1 was identified by means of spectroscopic methods including electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance spectroscopy (NMR). Compound 1 showed DPPH scavenging activity with SC₅₀ value of 15.94 µg/ml and moderate cytotoxic activity on four human cancer cell lines including mouth epidermal carcinoma (KB), liver hepatocellular carcinoma (Hep-G2), lung carcinoma (LU-1) and breast cancer (MCF7) with IC₅₀ values of 11.95, 13.75, 15.65 and 16,84 µg/ml, respectively. Huyen Tram Le Van Thong Nguyen Thi Thu Hien Dinh Copyright (c) 2020 Old Journal 140 61 64 https://jst.vn/index.php/old/article/view/569 The aim of this study is to isolate cellulose-degrading Actinomycetes. Twenty one isolates of cellulolytic Actinomycetes were isolated from different soil and woody habitats such as, leaves, straws and rotted wood collected in Hanoi and were divided into six color groups of colony: purple-violet, pink, white, green, grey and yellow. Cellulase production was indicated by the appearance of a pale halo on agar medium containing CMC as substrate around the agar piece with colony on using lugol as an indicator. Cellulase activities of isolates were determined qualitatively by measuring the diameters of halo zones. G1, D4 and G3, exhibited the maximum zones of halo around the agar piece with diameter of 40mm, 40mm and 39mm respectively. The abilities of degrading natural cellulose (straw, sugarcane bagasse) of these three strains open up potential application in agriculture. Lieu Ba Nguyen Thi Phuong Anh Hoang Thu Hien Pham Thi Hong Hau Le Copyright (c) 2020 Old Journal 140 65 70 https://jst.vn/index.php/old/article/view/570 The red dragon (Hylocereus polyrhizus) is a potential fruit for Vinh Phuc province. In order to develop red dragon fruit products, this study aimed to evaluate the nutritional value and determined the effects of heat treatment, pH and the antioxidant addition (ascorbic acid) as well as the storage condition (light exposure, room and dark conditions) on the stability of betacyanin - the main color compound in fruit juice. The results indicated that the Vinh Phuc red dragon fruit had 12.6 °Brix, pH = 4.72; contained high nutritional value with 15% dry matter, 9.60 g/100g in the total sugar content, 8.12 g/100g in reducing sugar content, 1.12 g/100g protein and 5.1 mg/100g in vitamin C content, and 32.70 mg/100g in total betacyanin content. The best heating condition for the stability of betacyanin in the fruit juice was less than 80oC. Betacyanin was stable in acidic conditions (pH 3 ÷ 6), especially in pH 4, but this stability rapidly decreased in neutral and alkaline pH (pH ≥7). The addition of ascorbic acid at a concentration of 0.2% increased the stability of betacyanin in the fruit juice even in light exposure. Betacyanin was more stable at 15 °C and in dark condition. Thu Trang Vu Thi Thao Nguyen Nguyen Van Hung Nguyen Tien Cuong Nguyen Quoc Tuan Hoang Thi Thao Nguyen Thi Hanh Nguyen Thi Hoai Duc Nguyen Ky Son Chu Van Thai Nguyen The Hung Nguyen Copyright (c) 2020 Old Journal 140 71 76 https://jst.vn/index.php/old/article/view/557 This paper presents results of an investigation of direct short-term impacts on industrial, commercial, and residential customers and costs incurred by local random electrical supply interruptions. The study used a direct survey in The Southern Power Corporation of the Electricity of Vietnam (EVNSPC) to collect customer assessments of electric service interruptions to analyze the costs. The variation in interruption cost with the characteristics of interruptions, such as duration, time of day, week of year, advanced warning, and reliability history, and with the characteristics of the users was also investigated. These results of surveys and interruption costs of customers are included in the paper. Viet Tien Le Copyright (c) 2020 Old Journal 140 1 4 https://jst.vn/index.php/old/article/view/558 During process of designing noncircular planetary gearing system, one of the most important tasks is synthesis of pitch lines of the gears with condition of preserving correct transmission function. In this work, the authors present a method for synthesizing pitch lines of the noncircular planetary gearing system based on given pitch line of the planetary gear. In comparison with previous experience-based methods, this work also sets the condition for the pitch line of the second sun gear, which will cover all the inside planetary gears. Moreover, the authors propose a synthesizing process of the pitch lines of the noncircular planetary gearing system. Hong Thai Nguyen Thanh Trung Nguyen Copyright (c) 2020 Old Journal 140 5 10 https://jst.vn/index.php/old/article/view/559 Non-circular gear units have been used in variable transmissions such as car wipers, CVT speed variants or steering mechanism in new car generations, etc. Until now, most scientists are only focused on non-circular gears with involute profile of a circle or a hyperbola when researching these gears. The Novikov-type profiles have not been mentioned. In this work, the authors use the Novikov gears and racks to generate the tooth profile of non-circular gears. To solve this problem for each pair of gears in a gear train, the tooth profile of the driving gear is formed by finding the envelope of a Novikov rack, while the tooth profile of the drive gear is formed using gear shaping method (with the driving gear used as the cutter) to ensure meshing ratio and to prevent undercutting. Based on that, the study provides a general procedure for the synthesis of Novikov non-circular gears. Hong Thai Nguyen Thanh Trung Nguyen Thuy Duong Nguyen Hoang Viet Nguyen Copyright (c) 2020 Old Journal 140 11 17 https://jst.vn/index.php/old/article/view/560 This paper examines dynamic characteristics of a pneumatic servo system and develops a suitable mathematical model for the system. In order to deal with these purposes, an experimental setup of the pneumatic servo system using a double acting pneumatic cylinder and two proportional flow control valves is considered. The operating characteristics such as the piston position, the pressures in the cylinder chambers, and the friction force are measured and analyzed. A mathematical model of the pneumatic servo system is proposed by taking the dead-zone and quickly exhausting characteristics of the valve and a dynamic friction model of the pneumatic cylinder into consideration. The results make clear the dynamic behaviors of the system and show that the proposed system model is appropriate. Xuan Bo Tran Copyright (c) 2020 Old Journal 140 18 24 https://jst.vn/index.php/old/article/view/561 Hand shape and size are important data to design gloves, especially tight-fitting leather gloves. In this study, using the direct measurement method to determine 37 hand measurements in straightening and clench positions of 270 female students in Hung Yen. The basic statistical characteristics of the hand measurements were determined by using excels and SPSS software. The hand size system of studied female students with 9 sizes, such as 3 sizes by hand circumference and 3 sizes by hand lengths corresponding to each size by hand circumference, has been developed. This size system meets 92.6% of studied students. This is an important data for designing comfortable leather gloves. When the hand grasped, its length increased to 9.7%, fingers length to 26.1%, circumference to 5.6%. This needs to be considered when choosing materials, designing tight-fitting leather gloves. Van Huan Bui Thi Hoa Nga Do Copyright (c) 2020 Old Journal 140 25 30 https://jst.vn/index.php/old/article/view/562 This paper presents the research results on influence of some technological parameters during the winding process: the winding speed Z1, the compressing force of the yarn tension Z2 and the distance from the top of the bobbin to the guide eye of balloon controller Z3 to the twist of yarn after the winding process. By using the orthogonal planning experiments with the support of the software NEMRODW 2007, the influence of three selected parameters of technology was determined to the twist of yarn after the winding process. The experimental regression function shows the relationship between the twist of yarn after the winding process and the three selected technological parameters are established for 100% cotton, Nm 34. This research results are the base for selection of the technological parameters to achieve the required twist (change of the twist) of the yarn after winding process. To achieve the twist of yarn increased by 7% compared to the twist before winding, the winding machine has the highest productivity, the technological parameters to be selected are: Z1 = 800m/min, Z2 = 30cN and Z3 = 14cm. Thi Thu Huong Gian Duc Trung Tran Copyright (c) 2020 Old Journal 140 36 39 https://jst.vn/index.php/old/article/view/565 In this research, we investigated the structural and morphological properties of cellulose from bamboo bambusa blumeana and poplar wood, obtained by sulfate cooking. Using an automatic fiber analyzer L&W Fiber Tester investigates the length, the width of the fibers, as well as the characteristics of shape factor, number of kinks in the fiber and some other properties. The results show that, compared with the cellulose fibers of hardwood pulp, the cellulose fibers of bamboo are longer (1.8 to 1.0 mm), with a smaller width (17 to 25.8 µm), more curved (shape factor 87.5 versus 92.5) and have a higher number of kinks in the fibers (0.42 vs. 0.29). Minh Khoa Hoang Thi Minh Phuong Nguyen Copyright (c) 2020 Old Journal 140 45 49