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Autonomous underwater vehicles are increasingly frequently used in the fields of ocean observation, data collection, and tactical surveillance. Underwater navigation and near real-time communication are the most important factors limiting the performance of these vehicles. In this article, an underwater acoustic communication and positioning system (UACPS) based on heterogeneous gliders is presented. The system consists of an acoustic wave glider and an acoustic underwater glider, and includes an ultrashort baseline and an acoustic modem. The program and communication protocol of the communication and positioning algorithm are independently developed, and the hardware circuit design of the communication and ultra-short baseline positioning, as well as the embedded surface wave gliders and gliders are independently implemented. Sea trial results indicate that the communication distance of the system is more than 3 km and the positioning error is less than 5%. With the further improvement of system performance, the low cost, long time, long distance and near real-time communication characteristics of our UACPS can be used to integrate multiple autonomous unmanned platforms as part of intelligent surveillance robot networks.

The installation error of an acoustic transceiver array is one of the important error sources in an ultra-short baseline (USBL) system. In a USBL system with a positioning accuracy of 0.5%, an installation error angle of 1° will lead to a positioning error of 1.7% times the slant distance. In this paper, a dual transponder-based installation angle error calibration method for USBL is proposed. First, the positioning errors induced by various installation angles are deduced and analysed using the linear measurement of seafloor targets. Then, an iterative algorithm is proposed that estimates the rolling alignment error, pitching alignment error, and heading alignment error, in that order. The simulation and experienced results show that, after three iterations, the estimates of the three alignment errors can converge quickly, all of the estimates converge to within 0.001° and the estimated values are very close to the true values. The horizontal positioning error caused by the installation error angle can be reduced by nearly 75%. The method has good effectiveness and robustness, and can greatly improve the positioning accuracy of the USBL system.

Graphite is widely used in molten salt reactors (MSRs) because of its excellent properties. However, the irradiation lifespan of graphite in MSR is much shorter than the life of a conventional nuclear power plant, which lowers the load factor and increases the economic burden. In this paper, to extend the graphite irradiation lifespan, one uniform radial fast neutron field was designed by changing the fuel distribution in different radial fuel channels, which is called continuous core zoning. A positive correlation correction algorithm was used to adjust the fuel volumetric fraction (VF) of each zone. The optimization was carried out among different reactor sizes and different thicknesses of the reflector to study flattening characteristics. After optimization, the difference in fast neutron flux between different zones of the flattened region was less than 1%. Compared to the unoptimized case, the peak value of the fast neutron flux can be most reduced by 48.6%. The study employed a single‐channel heat transfer model to investigate the temperature distribution within the both pre‐ and postoptimization core structure. The flow matching inlet condition and the average velocity inlet condition were considered. The results showed that to eliminate hot spots, a flow matching design is needed; otherwise, the temperature will rise greatly. Then the lifetime of graphite was calculated by combining fast neutron flux and temperature. Under average velocity inlet condition, graphite lifespan in CORE550‐20 increased from 11.4 years of the unoptimized core to 18.9 years of the optimized core, only representing a 66% enhancement due to higher temperatures. Under flow matching conditions, the lifespan of graphite in CORE450‐00 can be extended from 13.3 years of the unoptimized core to 26.8 years of the optimized core, indicating a 102% improvement. [ABSTRACT FROM AUTHOR]