The effect of formic-acid surface modification on the bond strength of the solid-state bonded interface of tin and copper has been investigated by SEM observation of the interfacial microstructures and fractured surfaces. Formic-acid surface modification was carried out by boiling a tin and a copper surface in formic acid for 600 s. Solid-state bonding was carried out in a vacuum chamber at a bonding temperature T of 403-473 K and a bonding pressure P of 7 MPa (bonding time: t ¼ 1800 s). The bond strength increased with an increase in the bonding temperature, independently of the formic-acid surface modification. Because of the surface modification, bonded joints were obtained at a bonding temperature that was 40 K less than the typical temperature required, and the bond strength was comparable to that of the base metal. When surface modification is applied, the oxide film is destroyed by the improved plastic deformability of the tin. Thus, the tensile strength of the joint is increased. On the other hand, when surface modification is applied, a high-tensile-strength joint is obtained at a low temperature because metallic tin and copper are exposed at the bond interface as a result of the decomposition of formate in the bond interface at a low temperature.
We developed a three-dimensional motion tracking system that displays trajectories as augmented reality in real time on a tablet device. The features of this system are as follows: (1) the three-dimensional trajectory can be observed from any direction. (2) Velocity and acceleration can be visualized as augmented reality.
The device consists of an Intel D435, a spatial recognition camera, and a Raspberry Pi 4 for data processing and transferring. The data are broadcasted to tablet computers, allowing simultaneous observation from multiple tablet devices. The sampling rate of the detection is 8 fps with a measurement error of 1.2%. Since even a general-purpose tablet device can be used to visualize trajectories as augmented reality with this motion-tracking system, it can be widely applied in the study of dynamics in physics from the junior high school to the university level.
Understanding electromagnetic induction, whose study is part of the middle school curriculum in Japan, is difficult for students. Thus, this study developed an augmented reality (AR) teaching aid for electromagnetic induction for middle school students. Magnetic lines are illustrated in three dimensions as an AR using conventional tablet PCs. Lessons were conducted with 127 middle school students, and the changes in their explanation of the principle of electromagnetic induction were investigated before and after using the teaching aid. The investigation revealed that only 3% of the students could explain scientifically the principle of electromagnetic induction before using the teaching aid; however, 63% of them were able to provide a scientific explanation after the AR teaching aid was applied.
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