Search

Due to the open underwater channels and untransparent network deployment environments, underwater acoustic networks (UANs) are more vulnerable to hostile environments. Security research is also being conducted in cryptography, including authentication based on asymmetric algorithms and key distribution based on symmetric algorithms. In recent years, the advancement of quantum computing has made anti-quantum attacks an important issue in the field of security. Algorithms such as lattice and SPHINCS+ have become a research topic of interest in the field of security. However, within the past five years, few papers have discussed security algorithms for UANs to resist quantum attacks, especially through classical algorithms. Some existing classical asymmetric and symmetric algorithms are considered to have no prospects. From the perspective of easy deployment in engineering and anti-quantum attacks, our research focuses on a comprehensive lightweight security framework for data protection, authentication, and malicious node detection through the Elliptic Curve and Hash algorithms. Our mechanism is suitable for ad hoc scenarios with limited underwater resources. Meanwhile, we have designed a multi-party bit commitment to build a security framework for the system. A management scheme is designed by combining self-certifying with the threshold sharing algorithm. All schemes are designed based on certificate-less and ad hoc features. The proposed scheme ensures that the confidentiality, integrity, and authentication of the system are well considered. Moreover, the scheme is proven to be of unconditional security and immune to channel eavesdropping. The resource and delay issues are also taken into consideration. The simulations considered multiple variables like number of nodes, attackers, and message length to calculate proper values that can increase the efficiency of this scheme. The results in terms of delay, delivery ratio, and consumption demonstrate the suitability of the proposal in terms of security, especially for malicious node detection. Meanwhile, the computational cost has also been controlled at the millisecond level. [ABSTRACT FROM AUTHOR]

Generalized frequency division multiplexing (GFDM) is a newly introduced technique for the wireless fifth-generation (5G) standard based on multicarrier filter bank theory, which has the advantage of flexibility in setting the number of subcarriers and subblocks. The application of GFDM in underwater acoustic (UWA) communication can take full advantage of the limited spectral resources, which is a prime limitation in UWA communication and will promote the development of UWA network technology. However, the multicarrier communication technique utilized in radio 5G communication offers difficulty in channel estimation, and the influence of a channel cannot be ignored especially in the UWA communication field. Therefore, GFDM cannot be implemented directly in UWA communication; to solve this problem, a system combining chaotic sequence spread spectrum technology with GFDM is proposed, which is a novel technique with high spectrum efficiency. Simulation and experimental results verified the effectiveness of the proposed system.

It is difficult for the conventional image compression method to achieve good compression effect in the underwater acoustic image (UWAI), because the UWAI has large amount of noise and low correlation between pixel points. In this paper, fractal coding is introduced into UWAI compression, and a fractal coding algorithm based on interest region is proposed according to the importance of different regions in the image. The application problems of traditional quadtree segmentation in UWAIs was solved by the range block segmentation method in the coding process which segmented the interest region into small size and the noninterest region into large size and balanced the compression ratio and the decoded image quality. This paper applies the classification, reduction codebook, and correlation coefficient matching strategy to narrow the search range of the range block in order to solve the problem of the long encoding time and the calculation amount of encoding process is greatly reduced. The experimental results show that the proposed algorithm improves the compression ratio and encoding speed while ensuring the image quality of important regions in the UWAI.

In order to improve the efficiency of chemical preparation of YBa2Cu3O7 s (YBCO) with long taps, the pyrolysis of traditional process preparing precursor film needs to be reduced to one step, so the crystallization process should be directly connected to the former without the cooling of pyrolysis. Replacing copper trifluoroacetate with copper isooctanoate can alleviate the centralized heat release and the contraction of the precursor film during pyrolysis. In this study,a suitable amount of boric acid was added into the precursor solution with total cation concentration of 1.0 mol/L. After a continuous heat treatment YBCO superconducting film was obtained. Utilizing the flow state of boric acid at 200-500 °C? boron oxide was doped into YBCO film which becomes denser and smoother by filling some pores. Compared with that one prepared by ?doped precursor solution under the same conditions, the former shows higher superconductivity. [ABSTRACT FROM AUTHOR]

Transcriptome analysis for the original Bacillus subtilis K1 strain and UV mutagenic strain UW07 with high yield of pectate lyase was implemented with RNA-seq. The function of genes was annotated and metabolic pathways were classified to look for different expression genes and classify these genes into related metabolic pathways to reveal the high-yield mechanism of pectate lyase in UW07. The results showed that 397 genes were up-regulated and 617 genes were down-regulated compared with the original strain. The up-regulated genes were mainly involved in ABC transporters, two-component system, biosynthesis of amino acids, and carbon metabolism.

The design principle and application of an adjustable spine prone frame are introduced. Adjustable spine prone frame is used in posterior lumbar surgery, during operation, X-ray can shoot fast and internal fixation implants can fix accurately, the vacant abdominal ensure normal respiratory and circulatory function, and the lumbar curvature can adjust conveniently. It meets the surgical position and care requirements, can prevent the complications effectively.