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In view of the problem that energy consumption of sensor nodes is fast and equipment life is cut caused by large amount of information transmission of wireless sensor network, a kind of compressed sensing image processing algorithm based on wavelet transform was put forward. The algorithm uses sym8 wavelet for image sparse and fragmental processing, and uses measurement matrix for adaptive sampling measurement, and finally reconstructs image through OMP algorithm and wavelet inverse transformation. The experimental results show that the proposed algorithm can obtain reconstructed image with high quality by lower sampling rate compared with traditional compressed sensing algorithm.

The impacts of Li+ replacement for Mn2+ on the structure, vacancy defects, and magnetic and dielectric characteristics of Mn1-xLixWO4 (x = 0.00–0.20) ceramics synthesized by solid-state reaction were investigated. The analysis of XRD and Raman results revealed that Mn1-xLixWO4 samples had single-phase monoclinic structure, and Li+ ions had partially replaced Mn2+ ions and induced lattice deformation and substitutional disorder in Mn1-xLixWO4. Positron annihilation lifetime spectroscopy indicated that Li+ replacement resulted in the reduction of vacancy size and the increase of vacancy concentration. The dielectric properties measurements showed that Li+ replacement significantly enhanced the dielectric constant of the Mn1-xLixWO4 samples. It could be observed from the magnetic properties measurements that Li+ replacement suppressed the AF1 phase, extended the existing temperature range of AF2 phase, and weaken the magnetization of Mn1-xLixWO4 system. The evolution of magnetic properties was related to vacancy defects, lattice distortion, chemical disorder, and magnetic dilution effect caused by Li+ replacement. [ABSTRACT FROM AUTHOR]

For problems that wireless transmission delay in tunnels of coal mine underground was random greatly and current time synchronization algorithms could not be applied directly in coal mine underground because of inability to determine delay distribution and parameters, an estimation method of transmission delay of time synchronization information for Internet of things was proposed based on passive measurement. A class of evaluation node is added to perception layer of Internet of things of coal mine underground for overhearing passively time synchronization packets among perception nodes to acquire transmission delay data. Then parameters under different distribution regularities are estimated by the evaluation nodes based on the maximum likelihood estimation method and optimal distribution regularity is determined according to Kullback-Leibler difference value. Parameter mutation is detected by using log-likelihood-ratio for determining whether the evaluation nodes send delay distribution regularity and parameters to sink nodes. The simulation results show that the method detects mutation of classification of delay distribution regularity and distribution parameters accurately.

For difficult transmission and storage of a large of video monitoring image data of coal mine underground, an image compression method was proposed which was based on improved compressive sending algorithm. Firstly, collected images data are spared by Coiflet2 wavelet transform principle. Secondly, the spared data is measured by measurement matrix to get measurement data. Finally, the images are refactored by orthogonal matching tracking algorithm and inverse transformation. The experimental results show that the method can effectively compress image and reconstruct the image.