Tạp chí khoa học và công nghệ

Thử nghiệm xác định lực tách dọc trục được dùng để đo độ bền khóa dọc trục của lót trong của ổ cối mô đun khớp háng toàn phần. Thử nghiệm này có thể được dùng như một phương tiện so sánh tính vẹn toàn của các cơ cấu khóa khác nhau của các ổ cối mô đun. Bài báo này trình bày việc thử nghiệm xác định lực đẩy dọc trục để tách lót trong ra khỏi vỏ ngoài của ổ cối mô đun được thiết kế cho người Việt Nam. Thử nghiệm này được thực hiện theo tiêu chuẩn ASTM F1820-13. Kết quả thử nghiệm cho thấy cần phải sử dụng một lực đẩy dọc trục trung bình là 2,14 kN để đẩy lót trong ra khỏi vỏ ngoài. Giá trị lực đẩy này tương đương hoặc cao hơn nhiều so với giá trị lực đẩy của một số ổ cối của một số nghiên cứu trước đây và một số nhà sản xuất ở Mỹ.

The International Union of Railways has decided to migrate railway communication technology from being GSM-based to LTE-based or LTE-R. As a leading country in LTE space, South Korea will launch the train control system based on LTE by 2016. To ensure the most reliable train operation in this system, a fully duplicated network structure with overlaid radio cells is needed. Existing methods and results often rely on a single network structure setup. Thus, in this paper, we introduce the design of an LTE-R train control communication with a duplicated network structure. We propose two different network structures with fully-overlapping cell arrangement and with partly overlapping cell arrangement, respectively for the system and discuss major problems, including handover and inter-cell interference.

The high penetration of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) can cause serious impact to the entire grid: from power plants to local distribution systems. In particular, the demand charging of EVs may vary over stochastic with time. Uncoordinated EVs charging may increase the load with all the time, which increases the peaks, even can possible produce super-high peak. Therefore, a comprehensive study on the impact of EVs to existing grid needs to be conducted to make the appropriate charging strategies with the future EVs demand. In this paper, the basic power allocation strategies for EVs as first come first serve strategy (FCFS), lowest state of charge (SoC) first strategy (LSF), equally allocation method (EAM) and shortest charging time first strategy (STF) are proposed. The simulation is completed using MATLAB. The result of the methods is analyzed, evaluated, and compared together.

Cathodic polarization technique was used for different Cr(III)-containing baths to explore the effect of inorganic additives on the mechanism of trivalent chromium electrodeposition. The presence of cations in the Cr(III)-containing bath can support a good condition for the diffusion of Cr3+ complexes from the bulk electrolyte to the cathode surface, thus improving the reduction of the Cr-complex. On the contrary, effect of anions was more complicated due to the appearance of additional reactions or an increase of viscosity in the bath. Results show that the morphology of the coating depends significantly on the addition of cations and anions. Quality of the coating is much better from the baths with the addition of Na+ or Mg2+ than addition-free, and only SO42- was acceptable to obtain a smooth morphology. In addition, higher current efficiency can be obtained from the baths added with cations of Na+ or Mg2+, and anion of SO42- in comparison with the other baths.

With the launch of the nationwide startup, the startup activities of students in universities are also very active. Universities play a very important role in stimulating the entrepreneurial spirit of the student as well as supporting successful student startups. The authors’ paper discusses the role of the university in the student’s start-up and offers some recommendations to further enhance the university’s role in student start-up.

This paper describes the nature of “viewpoints of interactive pedagogy” and its implications for a teaching process. Simultaneously, the authors suggest solutions to realize the viewpoints on the basis of evaluating the shortcomings and limitations in the practice of teaching occupational psychology while teaching students at Hung Yen University of Technical Education. Therefore, these viewpoints are aimed at improving the quality and effectiveness to teach subjects of technical teachers’ curriculum at the university

Upsetting force is a very important factor. It determines quality, efficiency and avoids defects when stamping tubes. In this study, the design of measuring system of upsetting tube force on the crank stamping machine was investigated. A principle of force sensor was placed in the mold system on the crank stamping machine. The principle of force sensor was based on piezo electricity, the deformation stamp was applied as a sensitive element for the sensor. The sensor has performed the function in receiving and transforming information about the variation of the force on the input into the voltage variation on the output. This output signal has been sent to the signal processing center and displays the measurement results. These results were used to compare and evaluate the results of the numerical simulation process. Also, the results of measurement of upsetting force with different cases were given and compared with the results of theoretical calculations

This paper presents the basis of theoretical research on propagation characteristics of hydro mechanical continuously gearbox. Research the characteristics of the mechanical transmission planetary gear type, plan actuator composite planet and analyze characteristics of each plan. Research the characteristics of the hydrostatic transmission, construction plans for communication interface with the planets to form stepless hydraulic actuator motor. Results analyzed articles and advantages and disadvantages of each alternative link here is the basis for choosing the plan to coordinate between the two types of mechanical actuators and hydraulic. Through this help choose the plan coordination between planetary transmission with hydrostatic transmissions to produce hydro-mechanical transmission with gear ratios appropriate range and meet the requirements of vehicles.

Structural optimization is potentially important to determine the chareristic of a new material, especially in nano-material science. Density functional theory, which have been applied extensively in recent years, emerges as an efficient method to study real materials applied in many desciplines of nano science and technology. In this report, we introduce biefly the theory and its application in the structural optimization by estimating the total energy of some materials. For the cubic structure materials, with a fit model, we find a curve to figure out the optimal point. For the system with two variations of lattice parameters, we compute total energies for obtaining a surface. Smooth surface is obtained by 2D spline fitting method. A discussion of the effect of approximations used in each case is given. The electronic structure calculation of SbxBi2-xTe3 is performed to clarify some aspects of its transport property and the effect of elecment substitution Sb-Bi, in which the spin-orbital coupling for relativistic-effect description has been included.

Research paper on convolutional neural networks, YOLOv3 algorithm, a deep learning model which is being widely researched and developed in the field of computer vision for real-time objects recognition. Applying this algorithm to build an identification system, analysis, and build a neural network to recognize traffic signs. The results of the paper are based on the model that has been built, tested, and evaluated. The results show that using the model in the image recognition problem is completely appropriate. In addition, they are the basis for the research and development of convolutional neural networks in recognition and controlling problems with real-time images, and videos.