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A key factor affecting the lifetime of wireless sensor networks(WSN) is its limited energy. Firstly, ratio of energy cost of different parts of a sensor node and time-dependent difference of data gathered is presented. Then, in order to prolong the lifetime of WSN under the limited energy, time-sensitivity of sensor is defined, sensors are classified based on it, scheduling for data gathering with time-sensitivity is presented and the ratio of energy saving is analyzed theoretically. Finally, the scheduling for data gathering based on time-sensitivity is implemented on Micaz platform, experimental data is gathered by simulation and measurement. The result illuminates that the scheduling based on time-sensitivity can reduce energy consumption by reducing data quantity transmitted, and it is more observable as the time-sensitivity become lower.

The travelling properties of laser-generated surface acoustic wave with broad bandwidth, which propagated on a sample with surface defects, have been investigated in theory. The numerical results of theoretical models with different defects indicate that the surface defects worked as low-pass filter for the travelling surface acoustic waves. The cut-off frequency of low-pass filter is linearly related to the depth of the defect, and decreased against the increasing depth of the defect. The amplitude of the travelling surface acoustic wave is seriously attenuated with increasing width of surface defect. The numerical results provide a theoretical basis for quantitative detection of the surface defects.