In this paper a new mechanica1 medel indicating the mechanical behaviour of main floor in longwall mining is proposed. In the medel the unfractured rnain floor is considered as an elasto plastic plate, and the combina...In this paper a new mechanica1 medel indicating the mechanical behaviour of main floor in longwall mining is proposed. In the medel the unfractured rnain floor is considered as an elasto plastic plate, and the combination of fractured blocks as a voussoir beam. Using the plastic hmit theory of plates, th limit load acting on rnain floor and the position of its largest deformation are gotten. The stability conditions for the key blocks of the voussoir beam are analysed by "S-R" stability theory. The results of the theoretical analysis are important for the study on the water inrush from seam floor.展开更多
To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio ...To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio （MSLR） is proposed for broadband beam-forming. This weighted method can be implemented by using the following steps. Firstly, optimize the spatial spectrum of each frequency unit by the second-order cone programming （SOCP）, and obtain the optimized spatial spectrum with lower side lobe. Secondly, construct weighting factors based on the MSLR of the optimized spatial spectrums to from weight factors. Lastly, cumulate the spatial spectrum of each frequency unit via the weight statistical method of this paper. This method can restrain the disturbance of background noise, enhance the output signal-to-noise ratio （SNR）, and overcome the difficulty of traditional four-dimensional display. The theoretical analysis and simulation results both verify that this method can well enhance the spatial spectrum of line spectrum units, restrain the spatial spectrum of background noise units, and improve the performance of the broadband beam-forming.展开更多
文摘In this paper a new mechanica1 medel indicating the mechanical behaviour of main floor in longwall mining is proposed. In the medel the unfractured rnain floor is considered as an elasto plastic plate, and the combination of fractured blocks as a voussoir beam. Using the plastic hmit theory of plates, th limit load acting on rnain floor and the position of its largest deformation are gotten. The stability conditions for the key blocks of the voussoir beam are analysed by "S-R" stability theory. The results of the theoretical analysis are important for the study on the water inrush from seam floor.
基金supported by the National Natural Science Foundation of China(Grant No.61372180)the National Key Scientific Instrument Equipment Development Project of China(Grant No.2013YQ140431)
文摘To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio （MSLR） is proposed for broadband beam-forming. This weighted method can be implemented by using the following steps. Firstly, optimize the spatial spectrum of each frequency unit by the second-order cone programming （SOCP）, and obtain the optimized spatial spectrum with lower side lobe. Secondly, construct weighting factors based on the MSLR of the optimized spatial spectrums to from weight factors. Lastly, cumulate the spatial spectrum of each frequency unit via the weight statistical method of this paper. This method can restrain the disturbance of background noise, enhance the output signal-to-noise ratio （SNR）, and overcome the difficulty of traditional four-dimensional display. The theoretical analysis and simulation results both verify that this method can well enhance the spatial spectrum of line spectrum units, restrain the spatial spectrum of background noise units, and improve the performance of the broadband beam-forming.
