The complex and changeable marine environment surrounded by a variety of noise, including sounds of marine animals, industrial noise, traffic noise and the noise formed by molecular movement, not only interferes with the normal life of residents near the port, but also exerts a significant influence on feature extraction of ship-radiated noise (S-RN). In this paper, a novel feature extraction technique for S-RN signals based on optimized variational mode decomposition (OVMD), permutation entropy (PE), and normalized Spearman correlation coefficient (NSCC) is proposed. Firstly, with the mode number determined by reverse weighted permutation entropy (RWPE), OVMD decomposes the target signal into a set of intrinsic mode functions (IMFs). The PE of all the IMFs and SCC between each IMF with the raw signal are then calculated, respectively. Subsequently, feature parameters are extracted through the sum of PE weighted by NSCC for the IMFs. Lastly, the obtained feature vectors are input into the support vector machine multi-class classifier (SVM) to discriminate various types of ships. Experimental results indicate that five kinds of S-RN samples can be accurately identified with a recognition rate of 94% by the proposed scheme, which is higher than other previously published methods. Hence, the proposed method is more advantageous in practical applications.

The faster and faster development of information network drives the progress of the society. The application of computer in people's daily life is becoming more and more widely. Computer science and technology do not only provide university libraries with new tools and means, but also change university libraries profoundly, from theory to practice, from technology to model. At present, although we see the gratifying situation of libraries, there are also some problems which are worthy of thinking, such as the disconnection between the theory and practice, ignoring theory research and too dependent on technology. Through the discussion of the important role of the computer technology in the university library development, as well as the negative impacts to the university library caused by the one-sided emphasis on computer technology, this paper puts forward that both the two are the relationship between theory and practice. The university library development cannot leave the computer technology, the library theory also decides the breadth and depth of the application of computer technology in the library field.