For a general case of three dimensional bounded region, we put forward a kind of fractional step characteristic difference schemes.

在考虑三维有界区域的一般情况下，提出了一类分数步长特征差分格式。

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By discussing a class of the neutral difference equation with several delay arguments, the author deduces a necessary and sufficient condition for the existence of bounded positive solutions.

考虑一类含有多个滞量的中立型差分方程，获得了该方程存在有界正解的一个充分必要条件。

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