Soap bubbles can be easily generated by varies methods, while their formation process is complicated and still worth study. A model about the bubble formation process was proposed in Phys. Rev. Lett. 116, 077801 recently, and it was reported that the bubbles were formed when the gas blowing velocity was above one threshold. However, after repeating these experiments, we found the bubbles could be generated in two velocities ranges which corresponded to laminar and turbulent gas jet respectively, and the predicted threshold was only effective for turbulent gas flow. The study revealed that the bubble formation was mainly influenced by the aerodynamics of the gas jet blowing to the film, and these results will help to further understand the formation mechanism of the soap bubble as well as the interaction between gas jet and thin liquid film.

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The interaction of MeV H 2 + molecular ions with thin layer graphene and graphite foils was studied by using a high-resolution electrostatic analyzer. A large number of fragment protons were observed at zero degree (along the beam direction) when the H 2 + beam was passing through the monolayer graphene foil, which indicates that the electron of the H 2 + molecular ions can be stripped easily even by the monolayer graphene foil. More trailing than leading protons were found in the energy spectrum, which means significant wake effect was observed in the monolayer graphene foil. The ratio of the numbers of trailing protons over leading protons first increased with the thickness for the much thinner graphene foils, and then decreased with the thickness for the much thicker graphite foils, which indicates that the bending effect of the wake field on the trailing proton varied with the foil thickness.

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The expansion and transportation of supersonic molecular beams is a complex process of molecular dynamics, and the related parameters are difficult to calculate accurately. Currently there is no rigorous theory to accurately predict the beam expansion process under specific valve conditions, and current researches are less concerned with the spatial evolution of supersonic molecular beam characteristics over long distance. In addition, time-of-flight mass spectrometry is not well suitable for supersonic molecular beam injection in the field of magnetic confinement fusion. Therefore, based on microphone measurements, the average velocities of several supersonic molecular beams (H₂, D₂, N₂, Ar, He, CH₄) in the process of free expansion and their evolutions in the far-field space (flight distance/nozzle diameter > 310) are studied in this work. The variations of velocity distribution with gas type, temperature, pressure and expansion distance are obtained. The results show that the velocities of H₂, D₂ and H_e beams account for only 54%, 60% and 68% of their ideal limit velocities, respectively, and their velocities decrease rapidly in the far-field space. The velocities of CH₄, N₂ and Ar beams are very close to their limit velocities, accounting for 85%, 92% and 99% respectively, and their velocities decrease slowly in the far-field space. And the results show that the velocities of the H₂ and D₂ beams increase with the source pressure, while the velocities of the other four molecular beams decrease slightly with the source pressure. And it is found that the velocity of supersonic beam without skimmer is negatively correlated with the square root of the molecular mass. For the effect of temperature on velocity, the results show that the velocities of H₂ and D₂ beams increase with the source temperature but are smaller than their limit velocities at given temperature, and the difference is larger for higher temperature. The results of this experiment provide basic data for controlling the parameters of the supersonic molecular beam by adjusting the temperature and pressure of the gas source, which will contribute to the application of supersonic molecular beams in fusion reactor fueling technology. And this study will contribute to further exploration of the evolution of supersonic molecular beam properties in the far-field space.