Molten metal droplet techniques are one of the important technologies for printing micro-metal parts. At present, the equipment developed for this technology faces some challenges, such as the ...requirement for a micro-oxygen environment during operation and a complicated manufacturing process. Consequently, a micro-air-pressure driven metal pellet spraying (MPS) 3D printing generator was designed and manufactured using the drop-on-demand technique, which uses simple and low-cost equipment in an atmospheric environment. A 2D axisymmetric model has been proposed to study the mechanism of droplet generation by using a micro-pneumatic MPS generator. In addition, a proprietary pneumatic MPS generator was also used to conduct droplet generation experiments. The validity of the proposed model was verified through the simulation results of the droplet pattern and droplet diameter, which were in good agreement with the experimental ones. The analysis shows that in the droplet injection forming process, surface tension is dominant for low viscosity liquids at a very small Ohnesorge number (Oh < 0.01). The surface tension was conducive to the maintenance of the molten form of the projectile. During droplet injection, the phenomenon of oblate–prolate oscillation occurs due to the non-uniform distribution of pressure inside the droplet. This phenomenon exerts an influence on the accuracy of the droplet flight trajectory and deposition position. This study serves as a good reference for selecting the suitable settings for producing metal droplets using the MPS generator.
Car-sharing economy has caused new driving safety and usability problems, which have not been well studied. This study aims at analyzing the effects of users age and the user experience (UX) of the ...car-sharing software (e.g., DiDi travel app) on overall usability and the level of distraction for drivers. To this end, 48 experienced Chinese drivers were recruited to perform various tasks with the car-sharing software using a driving simulator. The variables of driving safety and usability were analyzed by two-way analysis of variance (ANOVA) and independent sample Kruskal–Wallis nonparametric test. As expected, it was found that car-sharing software has a significant negative impact on driving distraction and usability. The overall performance of young drivers is better than that of the elderly, but it seems that young drivers are more likely to be led to errors by car-sharing software. In most aspects, experienced drivers perform better than inexperienced drivers and have a better in-depth understanding of car-sharing software weaknesses. However, inexperienced drivers performed better regarding braking time and interaction time. Although young inexperienced drivers performed worst in driving safety, they exhibited the lowest cognitive load and the highest interaction efficiency. The experience of using car-sharing software may improve driver’s ability to deal with driving distractions. The above conclusions provide theoretical support for optimizing the UX of car-sharing software and some references for driver’s screening and training.
The electrification of intercity railways plays a significant role in energy conservation and emission reduction. Research on passenger travel activities to optimize vehicle services can help to ...understand how best to improve passenger attraction and the use of intercity railways. In this study, we conducted observational research on two electrified intercity railways that were segregated by the attributes, leisure, and commute. The purpose was to determine the influence of line attribute, passenger gender, age, and seat availability on the types of activities performed onboard, with specific attention placed on the use of information and communication technology (ICT). Using structured observations, the travel multitasking activity data of 467 passengers were collected on two intercity railways in real-life situations. Using the chi-square test and binary logistic regression analysis, it was found that line attribute, gender, age, and seat availability have an impact on passenger activities. Differences in factors affecting passenger activities were also found according to the nature of their travel, whether for commute or leisure. Our results suggest that passengers on the leisure line prefer to engage in some social activities. For example, the probability of conversation among passengers on the leisure line was 3.47 times that of the commuting line, and the middle-aged and elderly travelers on this line were more likely to be in a daze and look around. The probability of taking a break for passengers on the commuting line was 3.625 times that of the leisure line, and passengers who were not seated on this line were found to be more likely to be idle. In addition, male travelers and young travelers preferred to engage in ICT immersive activities, such as using mobile phones, while women, middle-aged, and elderly travelers were more likely to engage in non-ICT immersive activities. Seated passengers were more likely to engage in simultaneous multitasking activities, rest, and conversations than passengers without seats.
The metal microdroplet deposition manufacturing technique has gained extensive attention due to its potential applications in microstructure fabrication. In order to fabricate components such as ...microchannel heat sinks and microchannel reactors, this paper investigates the interactions and influences between microdroplets and substrates, as well as between microdroplets themselves. The transient phenomena during the fusion of metal microdroplets in contact with the substrate and the formation of inclined columns, as well as the solid–liquid coupling and morphology formation processes during the collision between microdroplets, are analyzed. The influence of microdroplet spacing on the morphology of microchannels during their formation is specifically studied. A three-dimensional finite element numerical model for the deposition of metal microdroplets forming inclined pillars is established based on the volume of fluid (VOF) method. The model treats the protective gas around the microdroplet as an empty zone and the microdroplet as a single-phase fluid. Simulation analysis is conducted to investigate the forming patterns of unsupported microdroplets at different spacing and their impact on the fusion morphology of microchannel components. Building upon this, a series of validation experiments are conducted using a piezoelectric microdroplet generator to produce uniform aluminum alloy microdroplets with a diameter of approximately 600 μm. A method for fabricating metal microchannel structures is obtained, which is expected to be applied in fields such as scattering structures for high-power electronic devices and microreactors in microchemical fields.
The objective of this study was to determine the different effects of the arrow-pointing augmented reality head-up display (AR-HUD) interface, virtual shadow AR-HUD interface, and non-AR-HUD ...interface on autonomous vehicle takeover efficiency and driver eye movement characteristics in different driving scenarios.
Thirty-six participants were selected to carry out a simulated driving experiment, and the eye movement index and takeover time were analyzed.
The arrow pointing AR-HUD interface and the virtual shadow AR-HUD interface could effectively reduce the driver's visual distraction, improve the efficiency of obtaining visual information, reduce the number of times the driver's eyes leave the road, and improve the efficiency of the takeover compared with the non-AR-HUD interface, but there was no significant difference in eye movement indexes between the arrow pointing AR-HUD interface and the more eye-catching virtual shadow AR-HUD interface. When specific scenarios were considered, it was found that in the scenario of emergency braking of the vehicle in front, the arrow pointing AR-HUD interface and the virtual shadow AR-HUD interface had more advantages in takeover efficiency than the non-AR-HUD interface. However, in the scenarios of a rear vehicle overtaking the vehicle ahead and non-motor vehicles running red lights, there was no significant difference in takeover efficiency. For the non-motor vehicle invading the line, emergency U-turn of the vehicle in front, and pedestrian crossing scenarios, the virtual shadow AR-HUD interface had the highest takeover efficiency.
These research results can help improve the active safety of autonomous vehicle AR-HUD interfaces.
One of the important parts of the Internet economy is the car-sharing economy. Nevertheless, a few numbers of studies have been dedicated to the issues of safety of driving and usability resulting ...from the car-sharing software application. The current study aims at analyzing the effect of phone location and screen orientation on usability and safety of driving in Chinese drivers who use car-sharing software (e.g., UBER) and comparing the differences in the safety of driving and usability among various car-sharing tasks. To this end, 24 experienced Chinese Uber drivers were employed using a driving simulator, and three tasks of car-sharing software were investigated. The variables of driving safety and usability were analyzed by Repeat Measurement ANOVA as well as Two-way ANOVA. It was found that when the phone is located on the left side of the steering wheel, usability and driving safety were better compared to locating it on the right side. The orientation of the mobile phone screen had a major impact on usability, while its impact on driving safety was trivial. The left-portrait mode showed the best performance. No significant impact on usability was found in terms of tasks (T1: ordering; T2: route checking; T3: destination search), while tasks showed a significant effect on driving safety. Among these tasks, the T3 task showed the highest impact on driving safety. The T2 task was in the second rank, followed by the T1 task (T1 < T2 < T3). The findings obtained from Chinese participants were different from the findings obtained in Japan and the United States.
This finding can be used as a basis for the optimization design of ca-sharing software and as a foundation for improving the safety and usability of car-sharing software used by drivers in the car.
•Left side placement of the phone was better.•The best performance was obtained by left-portrait mode, while the worst was right-landscape mode.•The usability was influenced by the screen orientation, but the screen orientation had little impact on driving safety.•The tasks' order in terms of the effect on driving safety was T1 < T2 < T3.
This study examined the effects of color gradients and emojis in an augmented reality-head-up display (AR-HUD) warning interface on driver emotions and takeover performance.
A total of 48 ...participants were grouped into four different warning interfaces for a simulated self-driving takeover experiment. Two-way analysis of variance and the Kruskal-Wallis test was used to analyze takeover time, mood, task load, and system availability.
Takeover efficiency and task load did not significantly differ among the interfaces, but the interfaces with a color gradient and emoji positively affected drivers' emotions. Emojis also positively affected emotional valence, and the color gradient had a high emotional arousal effect. Both the color gradient and the emoji interfaces had an inhibitory effect on negative emotions. The emoji interface was easier to learn, reducing driver learning costs.
These findings offer valuable insights for designing safer and more user-friendly AR-HUD interfaces for self-driving cars.
As a large-scale public transport mode, the driving safety of high-speed rail has a profound impact on public health. In this study, we determined the most efficient multi-modal warning interface for ...automatic driving of a high-speed train and put forward suggestions for optimization and improvement. Forty-eight participants were selected, and a simulated 350 km/h high-speed train driving experiment equipped with a multi-modal warning interface was carried out. Then, the parameters of eye movement and behavior were analyzed by independent sample Kruskal-Wallis test and one-way analysis of variance. The results showed that the current level 3 warning visual interface of a high-speed train had the most abundant warning graphic information, but it failed to increase the takeover efficiency of the driver. The visual interface of the level 2 warning was more likely to attract the attention of drivers than the visual interface of the level 1 warning, but it still needs to be optimized in terms of the relevance of and guidance between graphic-text elements. The multi-modal warning interface had a faster response efficiency than the single-modal warning interface. The auditory-visual multi-modal interface had the highest takeover efficiency and was suitable for the most urgent (level 3) high-speed train warning. The introduction of an auditory interface could increase the efficiency of a purely visual interface, but the introduction of a tactile interface did not improve the efficiency. These findings can be used as a basis for the interface design of automatic driving high-speed trains and help improve the active safety of automatic driving high-speed trains, which is of great significance to protect the health and safety of the public.
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