ABSTRACT
When high-speed trains (HST) run in enclosed spaces such as long tunnels, the thermal accumulation of their suspension devices is continuous and cannot be effectively dissipated. In addition, previous experiments or simulations for the heat dissipation of HST in tunnel spaces did not consider the impact of sand. To clarify the impact of HWS-LT on the heat accumulation of HST equipment cabin, this study used the CFD method to numerically simulate the impact of different wind-sand flow concentrations or no-sand wind on the cooling of equipment in the long tunnel space. Firstly, the sand particles in the wind-sand flow gather at the tunnel entrance and enter the equipment cabin with the train as it enters the tunnel. This boundary condition is more in line with actual engineering situations. Secondly, both flows show asymmetric intrusion into the cabin due to the asymmetrical tunnel arrangement, but the sand particles in the wind-sand flow are affected by the vortices and tunnel walls, resulting in more asymmetric flow and some particles being trapped in the grids or filters, leading to outflow ρQ < inflow ρQ. Under the wind-sand flow condition, the temperature of some equipment surfaces shows more significant increases than under the no-sand wind. Finally, contrary to popular perception, the wind-sand flow carrying sand particles can dissipate heat more effectively than no-sand wind, and the higher the volume fraction φ within a certain concentration range, the better the heat dissipation effect. This is because the wind-sand flow has a higher specific heat capacity, which can remove some heat from the contact point between the sand particles and the equipment wall upon contact. The higher sand particle concentration increases the contact frequency and contact area between the sand particles and the equipment wall, and the heat transfer pathway and heat dissipation efficiency are improved.
ABSTRACT
Objective@#To provide ideas for the modernization of pulse diagnosis in traditional Chinese medicine (TCM) by comparing and analyzing the current status and trends of modern research on pulse diagnosis in China and abroad, using bibliometric and visualization software.@*Methods@#Modern research literature on pulse diagnosis was searched in China National Knowledge Infrastructure (CNKI) database from the foundation to May 31, 2023, and in Science Citation Index Expanded (SCIE) from January 1, 2003, to May 31, 2023. After further screening, Microsoft Excel 2019 was used for statistical analysis of publication volume, and CiteSpace (6.1.R6) and VOSviewer (1.6.20) softwares were employed for visual analysis of journals, countries/regions, authors, institutions, keywords, etc.@*Results@#This study included a total of 764 articles in Chinese and 1 459 articles in English. The publication trend of pulse diagnosis research in SCIE database showed an overall fluctuating upward trend, while it exhibited a fluctuating downward trend after 2007 in CNKI database. The volume of English research literature has consistently exceeded that of Chinese literature since 2009. Publications on pulse diagnosis research involved 74 countries/regions. The related journals covered various disciplinary fields, including mathematics, physics, chemistry, and computer science. The most prolific author in CNKI database was WANG Yiqin (Shanghai University of Traditional Chinese Medicine), while the highest number of publications was attributed to ZHANG David (The Hong Kong Polytechnic University) in SCIE database. High-volume institutions in pulse diagnosis research in China and abroad were predominantly TCM research institutions. However, comprehensive universities and other research institutions also made noteworthy contributions. In recent years, hot topics in the modernization of pulse diagnosis research in China included pulse waves, sensors, and artificial intelligence. Foreign research focused on pulse diagnosis systems, sensors, pulse feature extraction, pulse signal analysis, pulse detection, and efficiency of use.@*Conclusion@#Chinese scholars have shown notable participation and emphasis in the modernization research of pulse diagnosis, involving a wide range of disciplinary fields and indicating a characteristic of multidisciplinary cross-fusion development. The hotspots andtrends in the modernization of pulse diagnosis research primarily concentrate on the study of pulse condition and signal acquisition, the integration, development, and optimization of various algorithms with pulse diagnosis equipment, and the practical application research of existing objectified outcomes of pulse diagnosis.
ABSTRACT
As the main component of the tractor gearbox, the box has the functions of shifting operation and carrying the cab, it also carries part of the framework function. If the strength, stiffness, or vibration characteristics of the box do not meet the allowable requirements, large vibration and noise may occur, and even there is the possibility of fracture in some limiting conditions. To solve this problem, according to the structural parameters of a gearbox, the three-dimensional model of the box was established by using the three-dimensional modeling software Creo. According to the dangerous degree of the transmission load when the tractor is working normally, three vehicle working conditions are selected: a round of suspension conditions, farm tool lifting conditions, and emergency turning conditions. In addition, according to the transmission ratio of each gear meshing inside the gearbox, two gear conditions are selected: gear condition one and reverse gear condition one. The forces of the box under these extreme conditions are analyzed. The static analysis and modal analysis of the tractor gearbox are carried out by using the Static Structural module of ANSYS Workbanch. The deformation, equivalent stress distribution, and modal vibration frequency of the gearbox are tested. The topology optimization method is used to improve structural defects and reduce box quality. The results show that the weight of the optimized box reduces by 8.44%, the deformation decreased by 15.89%, and the equivalent stress decreased by 18.34%. The strength and stiffness of the box are improved, the quality is lightweight, the waste of resources is reduced, and the heat dissipation performance and fracture resistance of the box are enhanced.
ABSTRACT
The rail transit vehicle system is an important subsystem with the most frequent operation accidents and the most direct impact on passengers. Based on the particularity of the vehicle system and the complexity of the system, the hierarchical analysis method (AHP) is used to evaluate its safety. High-order judgment matrix often has inconsistency, and the judgment matrix consistency guarantee is the key to the hierarchical analysis method applied. Based on the hierarchical analysis principle, this paper corrects the inconsistency judgment matrix and realizes the optimization calculation based on the genetic algorithm. This paper constructs a vehicle system safety evaluation index system including 26 indexes at three layers and uses the fuzzy comprehensive evaluation method to evaluate the system safety level. The results show that the calculation results based on the improved AHP-GA are significantly better than that based on the conventional AHP method. The comprehensive evaluation conclusion of the case is "average", and the safety level of the vehicle system of the case enterprise needs to be strengthened.
ABSTRACT
For safety engineering majors, it is very important to cultivate the practical ability of professional talents. Due to the difficulty of conducting experiments in dangerous environments, a virtual simulation experiment teaching platform was established. The platform allowed students to understand the structure of the subway ventilation room, and master the control requirements of the ventilation system in the event of sudden fire, blockage, and failure in the subway. Its construction used technologies such as 3D modeling, human-computer interaction, and VR. To test the teaching effect of the simulation experiment platform, two indexes of operating skills and cognitive load were selected to study and analyze the experimental results of students. The research adopts the method of stratified sampling, 46 boys and 10 girls were selected from the first-year students majoring in safety engineering, and they were randomly divided into experimental group and control group, with 23 boys and 5 girls in each group. The experimental group used the simulation platform for teaching, while the control group used the traditional teaching method. The score of the assessment module in the platform was taken as the index of students' operating skills, and the cognitive load test was carried out by questionnaire to test the teaching effect. The test module scores showed that the average score of the experimental group was 32.79 points higher than that of the control group, and the results of the cognitive load test questionnaire showed that the experimental group scored 35.14% lower than the control group. The research shows that the virtual simulation experiment has a stronger teaching effect than the field experiment.
Subject(s)
Railroads , Computer Simulation , Female , Humans , Male , Students , TeachingABSTRACT
A new water quality assessment model was built based on projection pursuit technique. A great quantity of sample data was applied to increase the model's precision. A new genetic algorithm combined with conditional optimization method was proposed and applied to the model optimization, which could deal with global optimization problem with various restrictions effectively. The case study shows that this model can give an appropriate assessment of water quality. Moreover, it can determine the index weights in an objective way or provide information for decision makers, which is difficult for other assessment methods.
