http://stdjet.scienceandtechnology.com.vn/index.php/stdjet/issue/feed Science & Technology Development Journal - Engineering and Technology 2020-10-26T03:22:54+00:00 Mai Thanh Phong pvphuc@vnuhcm.edu.vn Open Journal Systems http://stdjet.scienceandtechnology.com.vn/index.php/stdjet/article/view/658 Simulation study on polishing of gear surfaces in non-Newtonian fluid 2020-10-26T03:22:51+00:00 http://stdjet.scienceandtechnology.com.vn/public/journals/2/article_658_cover_en_US.png Duc Nam Nguyen nguyenducnam@iuh.edu.vn Hùng Anh Lý lyhunganh@hcmut.edu.vn Cong Truyen Duong duongcongtruyen@iuh.edu.vn <p>The non-Newtonian fluid is one type of shear thickening fluid which applied to process the complicated products. In this study, the new method of shear thickening fluid polishing (STFP) was used to polish the alloy steel SCM435 gears and the principle and performance of polishing process were also introduced. In the polishing process, the inclination angle of gears was believed to be an important parameter that affects the pressure and surface quality at different position on the tooth surfaces because it determines the contact between the polishing fluid and the tooth surface of the gear. The influence of the inclination angles on the pressure distribution and characteristics of fluid flow was performed by simulation process. The inclination angles of 0, 4, 8, 12, 16, 20 and 24 degrees were chosen in this study. As a result, the best inclination angle of gears is about 16 degree in the machining process. The tooth surfaces of gear have been in contact with the polishing fluid and the produced pressure reaches of 14.88 kPa. In addition, the influence of polishing speed on pressure were carried out in this study when inclination angle was established about 16 degree. The produced pressure on tooth surfaces increased with increasing the polishing speed. The results indicated that the different polishing speed also greatly affects the surface quality and machining efficiency. Therefore, the suggested machining method can become a suitable processing method for polishing the complicated products.</p> 2020-10-22T22:35:36+00:00 ##submission.copyrightStatement## http://stdjet.scienceandtechnology.com.vn/index.php/stdjet/article/view/532 Energy-Efficiency Approach for Long Range Wireless Communication 2020-10-26T03:22:54+00:00 Le Cong Nga congngale@gmail.com Cuong Quoc Pham cuongpham@hcmut.edu.vn Tran Ngoc Thinh tnthinh@hcmut.edu.vn <p>According to recent researches, the wireless sensor networks (WSN) which consume low levels of energy become more and more popular nowadays, so the research trend of optimizing energy for WSNs is rapidly increasing. LoRa technology is a modulation technique that provides long-range transfer of information and low power consumes. Besides, LoRaWAN is a network protocol that optimized for battery-powered end devices. The LoRa and LoRaWAN can be considered a suitable candidate for WSNs, which can reduce power consumption and extend the communication range. In this paper, we studied adaptive mechanisms in the transmission parameters of the LoRa network and proposed an energy-optimized solution for the adaptive algorithm. This research not only introduced the reference hardware of a sensor node in WSNs but also conducted experiments on typical LoRa network infrastructure</p> 2020-10-17T00:00:00+00:00 ##submission.copyrightStatement##