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The impedance matching is essential in producing high-intensity acoustic waves. This paper studies the impedance calculation methods of modulators and double-chamber Helmholtz resonators based on fluid mechanics, aeroacoustics, and electro-acoustic analogy principles. The results: ① The impedance expression of the resonators is derived. ② The impedance variation law of the chamber volume, the stator size, the air supply pressure, the air supply flow, and the working frequency is calculated. ③ The impedance-matching design scheme of the two-chamber Helmholtz low frequency and high acoustic intensity generator is given. Based on the experimental results of the high acoustic intensity generating device that the author has manufactured in the closed space, the correctness of the impedance calculation and matching design scheme in this paper is verified. This method has guiding significance for the design of high-intensity acoustic generating devices in confined space. [ABSTRACT FROM AUTHOR]

The mitochondrial genome sequence ofGloydius saxatilisis analyzed and presented for the public for the first time. The genome was 17,218 bp in length and contained 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and 2 control regions. The overall base composition was A (32.3%), C (28.9%), T (25.8%), and G (13.0%). The base compositions presented clearly the A-C skew, which was most obviously in the protein-coding genes. The extended termination-associated sequence domain, the central conserved domain and the conserved sequence block domain are defined in the mitochondrial genome control region ofG. saxatilis. Mitochondrial genomes analyses based on MP, ML, NJ and Bayesian analyses yielded identical phylogenetic trees, indicating a close phylogenetic affinity of the thirteen Crotalinae species. It appeared that no less than two major phyletic lineages were present in Crotalinae. The main clades within the Crotalinae supported are: A clade including theProtobothrops.A clade (G. brevicaudus, G. ussuriensis, G. intermedius, G. saxatilis)with theOvophisas the sister taxon toProtobothropsand was supported by bootstrap values of 88%. The fourGloydiusspecies formed a paraphyletic group with the high bootstrap value (100%) in all examinations. [ABSTRACT FROM AUTHOR]