Arc welding processes, such as shielded metal arc welding (SMAW), metal inert gas (MIG), and tungsten inert gas (TIG), play an important role in industrial applications. To improve the efficiency of the exploitation of traditional welding systems, new technologies have been used. Virtual reality technology is one of them. The virtual reality (VR)-based welding system enables to increase the frequency of practice to help learners obtain welding experience to avoid errors that occur during actual welding processes. This paper presents a VR-based system for simulating three welding processes: SMAW, MIG, and TIG. The developed system includes hardware components and VR software installed on a computer. The change in the physical devices, such as moving the welding torch and the distance from the welding torch to the plates to generate the weld bead, will update in real time and appear on the virtual environment. The functionality of the developed system for simulating the welding processes, such as in the real welding environment, was tested successfully. For implementing the system, welding speed and the distance from the welding torch to the plates are important process parameters, which determine the weld size or the weld formation. In this research, the ranges of the welding speed are 70 ÷ 120 mm/min; 240 ÷ 460 mm/min; and 250 ÷ 450 mm/min for the SMAW, TIG, and MIG processes, respectively. These values were tested experimentally. The distance from the welding torch to the plates to display the weld joint is 1.5 ÷ 5 mm. Outside of this range, no weld joint is formed. The welding widths are 4.4 ÷ 12.9 mm, 7.1 ÷ 12.4 mm, and 7.4 ÷ 11.3 mm for the SMAW, TIG, and MIG processes, respectively.

Optimal Placement of Phasor Measurement Unit for Observation Reliability Enhancement Phasor measurement unit (PMU);Optimal placement;Local search algorithm (LSA);Modified weighted adjacent matrix;Observation reliability; Phasor Measurement Unit (PMU) placement is a crucial problem for State Estimation (SE) of the power system, which can ensure that the power network is fully observed. Further, the observation reliability problem of the system has been concerned in the operation conditions. In this paper, based on modified weighted adjacent matrix ($A_w$), an optimal placement method is proposed to solve simultaneously two problems involving the optimal PMU placement problem and the observation reliability enhancement problem of the system. The purpose of the proposed method is to achieve both the minimum total cost and the maximum observation reliability, with a focus on increasing the security of observability, strengthening the observation reliability of buses as well as enhancing the effectiveness of redundancy. Simulations on IEEE 14, 24, 30 and 57 bus test systems are presented to justify the methodology. The results of this study show that the proposed method is not only ensuring the power network having the observability effectively but also enhancing significantly the observation reliability. Therefore, it can be a useful tool for SE of the power system.

This paper presents an investigation into harmonic distortion and voltage fluctuations caused by the 25 kV–50 Hz railway traction power supply system and their impact on the power quality of the Vietnamese electrical grid. A detailed traction load model representing train operating modes under Vietnamese conditions is developed in Matlab/Simulink. The study focuses on analyzing key power quality indices, including voltage fluctuations and harmonic distortion at the Point of Common Coupling (PCC). Simulation results illustrate that traction loads generate significant harmonic components and noticeable voltage sag during acceleration. These findings provide a technical basis for selecting appropriate compensation solutions such as D-STATCOM or energy-storage-integrated converters for future railway electrification projects. Furthermore, the study contributes essential insights for planning and integrating 25 kV railway systems into Vietnam’s power grid with improved power quality and operational reliability.

The paper presents the results of research and experiment in designing a control card for an auxiliary generator. Designing the card is based on the digital signal processing technology instead of the outdated analog one. The card has been manufactured, tested under long-term practical conditions and accepted to use for Vietnam Railway Industry. In addition, this study also plays an important role in the research direction of designing a control computer for the locomotive while performance of the locomotive depends entirely on this computer. The research results not only has implications in step by step of designing, localizing the locomotive's computer, but also determining methods for designing, testing microcontrollers and power electronics in the control system of locomotives.