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Water jet propulsion is a crucial technology for ships and underwater vehicles. A high-pressure water jet propulsion system was proposed in this paper. The fundamental thrust theory of this system was studied and the influence of cavitation on the thrust was investigated. First, the mathematical model of thrust based on momentum equation coupled with cavitation theory was established. Then, the performance of cavitation two-phase flow field was simulated through computational fluid dynamics (CFD), and the thrust was calculated according to these simulation results. Finally, experiments were conducted on a test rig to study its force performance. The experimental results showed that the maximum thrust reached 4000 N with a 16-mm nozzle at the flow rate of 1200 L/min. The experimental results were both higher than the simulation and the calculation results. The theoretical force model coupled with the cavitation model was better matched with the experimental results.

Counterfeits in the medicine market make the authentication of snakes used for Chinese medicine a challenge to Chinese drug regulatory control agencies. This paper explores existing methods that can be used to quickly and accurately distinguish Zaocys (Z. dhumnades) from its counterfeits for routine identification of snake meats in food and drug control laboratories. In this research, the Cytochrome Oxidase I (COI) fragments of 51 samples from 17 species of snakes were amplified using Polymerase Chain Reaction (PCR) and sequenced. The inter- and intra-specific variations of COI sequences were analyzed and compared based on Kimura-2-parameter (K-2P) distances; the minimal interspecific K-2P distance was 0.0934, which was bigger than the maximum intraspecific K-2P distance in Z. dhumnades (0.0523), indicating that Zaocys can be separated from its counterfeits. The Neighbor-Joining (N-J) tree of the snakes was constructed and the results show that snakes of the same species cluster with 100% bootstrap values. Since the Zaocys and its counterfeits are of different species, they can be distinguished using the N-J tree method. Another 10 samples of Zaocys from markets and drug stores were identified at the species level, among which 5 samples were proven to be the counterfeits--Ptyas korros.