Trang: 153-161 Pham Trong HoaTóm tắtEffect of oil temperature and viscosity on the ring gear orbit in the internal gear motor and pump is analyzed in this study. The mobility method is used to calculate the ring gear orbit. The mathematical model of oil viscosity and temperature is then integrated into the mobility method. The simulation results point out that the oil temperature and viscosity have great effect on the eccentricity, position angle and minimum oil film thickness. The metal - to - metal contact phenomenon occurs if internal gear motor and pump operates under high values of oil temperature or low values of oil viscosity conditions.
A new variant of radial visualization for supervised visualization of high dimensional data
Trang: 162-172 Tran Van Long, Thi Nguyen DinhTóm tắtRadial Visualization technique is a non linear dimensionality reduction method. Radial Visualization projects multivariate data in the 2-dimensional visual space inside the unit circle. Radial Visualization supports display both the samples and the attributes that provides useful information of data structures. In this article, we introduced a new variant of Radial Visualization for visualizing high dimensional data set that named Arc Radial Visualization. The new proposal that modified Radial Visualization supported more space to display high dimensional datasets. Our method provides an improvement in visualizing cluster structures of high dimensional data sets on the Radial Visualization. We present our proposal method with two quality measurements and proved the effectiveness of our approach for several real datasets.
Optimization of milling process parameters for energy saving and surface roughness
Trang: 173-183 Quoc-Hoang Pham, Xuan-Phuong Dang, Tat-Khoa Doan, Xuan-Hung Le, Lan-Huong Luong Thi, Trung-Thanh NguyenTóm tắtImproving the technical parameters of the machining process is an effective solution to save manufacturing costs. The purpose of this work is to decrease energy consumption (EC) and average surface roughness(ASR) for the milling process of AISI H13 steel. The spindle speed (S), depth of cut (a), and feed rate (f) were the processing inputs. The milling runs were performed using the experimental plan generated by the Box-Behnken method approach. The relationships between inputs and outputs were established using the response surface models (RSM). The desirability approach (DA) was used to observe the optimal values. The results showed that the reductions of EC and ASR are approximately 33.75% and 40.58%, respectively, as compared to the initial parameter setting. In addition, a hybrid approach using RSM and DA can be considered as a powerful solution to model the milling process and obtain a reliable optimal solution.
A driver drowsiness and distraction warning system based on raspberry Pi 3 Kit
Trang: 184-192 Dao Thanh Toan, Thien Linh VoTóm tắtIn this article, a system to detect driver drowsiness and distraction based on image sensing technique is created. With a camera used to observe the face of driver, the image processing system embedded in the Raspberry Pi 3 Kit will generate a warning sound when the driver shows drowsiness based on the eye-closed state or a yawn. To detect the closed eye state, we use the ratio of the distance between the eyelids and the ratio of the distance between the upper lip and the lower lip when yawning. A trained data set to extract 68 facial features and “frontal face detectors” in Dlib are utilized to determine the eyes and mouth positions needed to carry out identification. Experimental data from the tests of the system on Vietnamese volunteers in our University laboratory show that the system can detect at realtime the common driver states of “Normal”, “Close eyes”, “Yawn” or “Distraction”
Trang: 193-200 Cuong Manh TranTóm tắtWe report on the electron trapping mechanism in a multi-level organic field effect transistor (OFET) memory using Lithium-ion-encapsulated fullerene (Li+@C60) as the floating gate. Based on the estimation of trapped electron number per each Li+@C60 molecule when a programming voltage was applied, the active domain of the floating gate was determined to be the surface of the Li+@C60 domain. An analysis of the cyclic voltammetry indicated that each Li+@C60 molecule can trap electrons at the trapping energy level of -4.94 and -4.49 eV. The number of trapped electron was confirmed by the ultraviolet-visible spectroscopy (UV-Vis).
Trang: 201-213 Nguyen Hoang-Tung, Pham Diem-HangTóm tắtThe involvement of private investors in public works has been widely-known under the scheme of Public-Private Partnerships (PPP) world-wide. Although being started in early years of the twenty-one century, the PPP scheme in Vietnam is still waiting for its booming period due to an incomprehensive regulation system. As of an approval of some important PPP decrees, the period of 2010-2018 is considered as a remarked period for the PPP development in Vietnam, especially in transport sector. Using the neural network approach, this study contributes to the literature by providing an insight of 48 build-operate-transfer (BOT) transport projects completed in the period. Findings of this study are meaningful to the field because they highlight several influenced factors of the project preparation phase those affect total completed construction time of the investigated projects.
Trang: 214-224 Ngoc Dung Bui, Dzung Lai Manh, Vu Hieu Tran, Binh T. H. NguyenTóm tắtVideo surveillance is emerging research field of intelligent transport systems. This paper presents some techniques which use machine learning and computer vision in vehicles detection and tracking. Firstly the machine learning approaches using Haar-like features and Ada-Boost algorithm for vehicle detection are presented. Secondly approaches to detect vehicles using the background subtraction method based on Gaussian Mixture Model and to track vehicles using optical flow and multiple Kalman filters were given. The method takes advantages of distinguish and tracking multiple vehicles individually. The experimental results demonstrate high accurately of the method.
Trang: 225-235 Ngo Dang Quang, Mai Dinh LocTóm tắtAn inspection of a tidal river concrete bridge in the Mekong River Delta discovered a large number of map cracks in most piers within the tidal range. These map cracks distribute nearly vertically and horizontally with a distance of about 15 and 20 cm. Many of them have a width over 1 mm and a depth exceeding the thickness of the reinforcement protection concrete layer. Considering the location and the pattern of cracks, the most acceptable hypothesis on their cause was the strain gradient in concrete induced by the change of moisture content during tide rise and fall, i.e. by the effect of wet – dry action. To verify this hypothesis, experiments on the time dependent change of concrete moisture content and volume were conducted. Based on the results of these experiments, a computer simulation was performed. The simulated crack map and pattern agreed very well with the observed ones. With the obtained results, it is reasonable to conclude that strain gradient in pier concrete induced by the wet – dry action may one of main causes of cracks in such bridge piers
