RESUMO
Wireless sensor network deployment should be optimized to maximize network coverage. The D-S evidence theory is an effective means of information fusion that can handle not only uncertainty and inconsistency, but also ambiguity and instability. This work develops a node sensing probability model based on D-S evidence. When there are major evidence disputes, the priority factor is introduced to reassign the sensing probability, with the purpose of addressing the issue of the traditional D-S evidence theory aggregation rule not conforming to the actual scenario and producing an erroneous result. For optimizing node deployment, a virtual force-directed particle swarm optimization approach is proposed, and the optimization goal is to maximize network coverage. The approach employs the virtual force algorithm, whose virtual forces are fine-tuned by the sensing probability. The sensing probability is fused by D-S evidence to drive particle swarm evolution and accelerate convergence. The simulation results show that the virtual force-directed particle swarm optimization approach improves network coverage while taking less time.
RESUMO
In power ultrasonic and underwater acoustic fields, the ultrasonic treatment efficiency of vibration system can be improved significantly when vibration system is driven by the multi-frequency longitudinal transducer, and the performance of vibration system is determined by the multi-frequency characteristics of transducer. In this paper, using electromechanical equivalent circuit method, the multi-frequency characteristics of a longitudinal ultrasonic transducer with a stepped horn are studied for the ultrasonic vibration system optimal design. The expressions of the input impedance and the velocity amplification ratio of the transducer are obtained. The relationships between the electromechanical coupling coefficients, the velocity amplification of the multi-frequency transducer and the excitation position of the piezoelectric stack, the size of the stepped horn are analyzed. Combined with the finite element analysis of the transducer's key performance, the optimal design parameters of the multi-frequency transducer are given. Finally, the electromechanical properties of the multi-frequency transducer are tested experimentally, the theoretical analysis and finite element results are verified well.
RESUMO
It is well-known that geomagnetic fields have multiple components or parameters, and that these geomagnetic parameters are related to each other. In this paper, a parameter selection method is proposed, and this paper mainly discusses the correlation of geomagnetic field parameters for geomagnetic navigation technology. For the correlation analysis between geomagnetic parameters, the similarity calculation of the correlation coefficient is firstly introduced for geomagnetic navigation technology, and the grouped results are obtained by data analysis. At the same time, the search algorithm (Hex-path algorithm) is used to verify the correlation analysis results. The results show the same convergent state for the approximate correlation coefficient. In other words, the simulation results are in agreement with the similarity calculation results.