This paper is from the abalysis of Donald·Worster’s monograph“Nature’s economy: a history of ecological ideas”start, reveal Worstet’s eco-philosophy thoughts, pointing out that“philosophy basis”is human being and nature are interdependent community,“historical concept”is interaction history of human being and nature, value principle is nature’s“internal vable”and human obligation unity.

Waters'sociological perspective and Safety/Security-sociology;

The classical method for the digital Butterworth filter design is to work out corresponding analog filter first,then obtain the digital Butterworth filter from the bilinear transform,therefore the traditional method relies on the analog filter,and cannot obtain the zeros-poles plot equal filter.

In order to make the digital filter to maintain the frequency characteristic of the original analog filter,a expression for the prewarping is derived according to the definition of the bilinear transform,and a low-pass Butterworth digital filter is designed.

Here, Butterworth-respond method is adopted to approach ideal characteristic, and the rank order of the filter showed to be the main factor that influences a low-pass filter accuracy.

Because of the huge datasheet required by normal method, abundant calculation amount in Eigenvector improved method and not accurate enough coefficients in Walters improved method, we proposed a more simple and convenient method th.