This paper discusses the nonlinearity of fish acoustic signals by using the surrogate data method. We compare the difference of three test statistics-time-irreversibility T rev, correlation dimension D2 and auto mutua...This paper discusses the nonlinearity of fish acoustic signals by using the surrogate data method. We compare the difference of three test statistics-time-irreversibility T rev, correlation dimension D2 and auto mutual information function I between the original data and the surrogate data. We come to the conclusion that there exists nonlinearity in the fish acoustic signals and there exist deterministic nonlinear components; therefore nonlinear dynamic theory can be used to analyze fish acoustic signals.展开更多
该文介绍一种可对声学多普勒流速剖面仪(acoustic Doppler current profiler,ADCP)宽带模式流速进行现场校准的方法。通过接收ADCP发射的宽带信号,经处理后回发带有频偏和时域延拓的信号以模拟不同水层流速信息,并以回发信号相对原始信...该文介绍一种可对声学多普勒流速剖面仪(acoustic Doppler current profiler,ADCP)宽带模式流速进行现场校准的方法。通过接收ADCP发射的宽带信号,经处理后回发带有频偏和时域延拓的信号以模拟不同水层流速信息,并以回发信号相对原始信号的频偏值为溯源量实现ADCP径向流速的校准。采用数字上变频的方式提高信号处理的频率精度,使其满足小流速的校准要求,拓宽测量下限。搭建校准装置在开阔海域开展校准实验,在0.02~1 m/s范围内进行径向流速的校准并进行测量不确定度评定,在测量范围内的测量不确定度为2.2 mm/s(k=2)。与采样间隔缩放法作比对,校准结果表明不确定度显著减小,验证方法可行。展开更多
文摘This paper discusses the nonlinearity of fish acoustic signals by using the surrogate data method. We compare the difference of three test statistics-time-irreversibility T rev, correlation dimension D2 and auto mutual information function I between the original data and the surrogate data. We come to the conclusion that there exists nonlinearity in the fish acoustic signals and there exist deterministic nonlinear components; therefore nonlinear dynamic theory can be used to analyze fish acoustic signals.
