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.
Dynamic modeling and analysis of a bistable piezoelectric cantilever power generation system are presented. Firstly, a magnetic force model is established which could induce bistability, and the force mathematical expression between the two magnets is given. Secondly, a lumped parameter model of piezoelectric cantilever power generation system is built, and the range of distance between the two magnets is analyzed while the bistable phenomenon occurs. Thirdly, the response characteristics of the system are studied numerically. The results show that the beam undergoes large-amplitude motion at low frequency and low amplitude, and that the voltage response has a broadband. The system has high energy escaped from potential well when excitation amplitude imereases. Finally, the result is verified experimentally. This study provides a theoretical basis for the design and application of bistable piezoelectric cantilever power generation system.
As one kind of current main power sources, internal combustion engines require high-reliability to ensure mechanical systems working well in normal operation. This paper studies vibration signals in order to detect multiple types of faults by a single channel signal. First, for the decomposition level of variational mode decomposition (VMD) which needs to be chosen non-automatically, this paper analyzes the features of various faults and optimizes the iteration initial values of center frequency so as to reduce the adverse effect of inappropriate decomposition level. Moreover, considering that VMD cannot decompose different signal sources in the same frequency, robust independent component analysis (ICA) is an excellent method to overcome this challenge. Then, the fourth-order cumulant of restructured signals from VMD and robust ICA is taken as fault indexes. Finally, because of the high error rate of original fuzzy C-Mean clustering, Euclidean distance between test points and cluster center of fuel injection failure is taken as a fault detection threshold in order to achieve high-recognition rate. In conclusion, through optimizing several algorithms, the purpose of detecting multiple types of faults by single channel signal is achieved in the current research.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.