客厅里残留的痕迹是一些冰冷而沉重的、不可逆转的“时间”符号，涂写着一个人“回忆”中影像。
The residual marks in the livingroom are cold and heavy symbols of time that represent some image in one's recall.
一个实方阵a称为是S2NS阵，若所有与A有相同符号模式的矩阵均可逆，且它们的逆矩阵的符号模式都相同。
A square real matrix a is called an S2NS matrix, if every matrix with the same sign pattern as a is invertible, and the inverses of all such matrices have the same sign pattern.
构造了一类符号可逆图，并给出了这类图的符号逆图是平衡图的充要条件。
We now construct a class of signed invertible graphs, and obtain the condition of equivalence of their signed inverse graphs′being balanced graphs.
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