Damage evolution law of coal-rock under uniaxial compression based on the electromagnetic radiation characteristics

Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered residual strength. The applicability and accuracy of the model were verified through experiments. The results show that coal-rock damage evolution consists of four periods. The first period is from the beginning of compression to nearly 20% of the stress peak value, during which the damage variable changes stably about 0.1, and accordingly a few of electromagnetic radiation signals emerge. The second period is from about 20% to 70% of the stress peak value. The damage has stable development, and the parameter of electromagnetic radiation characteristics turns larger continuously with the increase of stress. The third period is when the damage has accelerated development, the coal-rock was broken which result from sharp increasing of the damage variable, meanwhile a great quantity of electromagnetic radiation signals emerge. The fourth period is after the coal-rock fracture, during which the damage variable corresponding to the parameter of electromagnetic radiation characteristics has a stable development. This research has great academic and realistic significance for further studies the electromagnetic radiation characteristics of coal-rock under loading and damage and the forecasting of coal-rock dynamic disasters.

Compressive sensing in wireless sensor network for poultry acoustic monitoring

A wireless acoustic sensor network was realized using wireless sensor nodes equipped with microphone condensers,in which its sensor nodes were configured to capture poultry sound data and transmit it via the network to a collection point.A high performance computer can process these large volumes of animal audio signals under different behaviors.By performing data signal processing and analyzing the audio signal,poultry sound can be achieved and then transformed into their corresponding behavioral modes for welfare assessment.In this study,compressive sensing algorithm was developed in consideration of the balance between the power saving from compression ratio and the computational cost,and a low power consumption as well as an inexpensive sensor node was designed as the elementary unit of poultry acoustic data collecting and transmission.Then,a Zigbee-based wireless acoustic sensor network was developed to meet the challenges of short transmission range and limited resources of storage and energy.Experimental results demonstrate that the compressive sensing algorithm can improve the communication performances of the wireless acoustic sensor network with high reliability,low packet loss rate and low energy consumption.

Method based on broadband compressed pulse superposition to measure properties of underwater acoustic materials

A method is proposed for the measurements of the performances of underwater acoustic finite sized large area material samples in a free field by using broadband pulse compression technique. As the result of which, the low-frequency cutoff of the standard tests is obviously reduced, and the broadband measurements are also realized. The experimental system provides measurements of complex reflection and transmission coefficients at continuous frequency points. From the data one can obtain the following acoustic parameters: echo reduction and insertion loss, absorption and attenuation coefficients, etc. The measurements are performed for two actual panels with the size 1 m x 1 m in the frequency range from 2-20 kHz.