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Firstly, a numerical computation model of submarine radiation noise was established to obtain the radiation noise of the submarine, which was compared with the experimental results, thus verifying the validity of the model. As indicated by the computational result, the submarine fairwater played a significant impact on radiation noise at the front section, whose structure was therefore necessary to be studied. In the paper, there were several different type submarine fairwaters. Large eddy simulation (LES) and boundary element method (BEM) were applied to conduct the numerical computation for the vortex flow field and acoustic characteristics of the original fairwater, the fairwater with fillet and the streamline fairwater. Furthermore, the impact and suppression effect of the fairwater’s type on wall pressure fluctuations and flow-induced noise were analyzed. As shown from the research, the vertical fairwater with fillet or the streamline fairwater can significantly improve the flow quality, thus considerably reducing the pressure fluctuations and flow-induced noise. The paper is conductive to the academic research of flow noise of submarine as well as the new submarine design in the future.

Availability is essential index for strategic weapons in storage mission. Spare parts replacement is an effective way to improve system storage availability. Normally, the performance degradation of spare parts before replacement is hardly considered in traditional instantaneous availability model. We established a instantaneous availability model using backward equation of semi-Markov Process (SMP) when considering the degradation time of spare parts before replacement. Our analysis indicated that availability had been great effect on when the performance degradation of spare parts is considered. An example is shown to express that this model could help policymakers to choose more suitable supporting plan.

As most Mutual Information method is limited to the correlation analysis between discrete variables in majority and tendency of choosing the characteristic variables with multi-values so far, in this paper we propose a new approach based on Mutual Information to measure the correlation of discrete variables and continuous variables. Then we take the fire control system of aircraft for example to calculate the correlation between fault types and monitor data indexes, and finally find the fault symptom classes.

Complicated structure of complex system makes it difficult to analyze and evaluate its reliability. Here we propose a method to calculate the importance of complex system components using a technique of Bernoulli State Variables (BSV). The models of three reliability importance, which describe the importance of each component, are proposed. Our studies show the method is suitable for complex artificial systems, and we proved the method can be used for maintenance decision and failure diagnosis though an example.

Safe landing for spacecraft on moon or the other planets is the basic premise for carrying on field survey and sampling research. When it comes to the spacecraft safe landing, the environment the spacecraft confronts becomes more complex. So the selection of landing area would influence the success landing probability of the spacecraft directly. The paper stands in reality and takes the factors such as craters and stones into account abundantly, which affect safe landing for spacecraft. Considering of the radiuses of obstacle spots (craters and stones) and the edge conditions of predestination landing area, we could find out the optimal landing area with the help of Delaunay Triangulation.