不可定向的曲面

Theorem Let M be a orientable or non-orientable closed surface, and f a C°-flow whose every singular point is isolated. Then f has POTP if and only if the following three conditions hold

定理 设M是任一个可定向或不可定向的闭曲面，f是M上任一个奇点均孤点的C〓-流，则f具有伪轨跟踪性质的充分必要条件是

Using combinatorial thoughts and topological methods,a closed curve system that contains the most number of non-contractible,pair-wise disjoint and pair-wise non-homotopic closed curves on the orientable surface is investigated.

利用组合数学的思想、拓扑的方法研究在可定向曲面上，一类含有个数最多的不可收缩的、两两不相交、互不同伦的圈系统及其性质，得出了关于这些圈的一些拓扑定性性质，并给出这些圈在曲面上的位置分布。

Secondly, we investigate C°-flows on orientable closed surfaces having POTP, and obtain a necessary and sufficient condition of such flows.

剖析了这些轨道的邻域的轨线结构，还考虑了经过Poisson稳定点及几乎周期点的横截圈和相应的回归映射，其中本文讨论了可定向闭曲面上具有伪轨跟踪性质的C〓-流，得到了可定向闭曲面上C〓-流具有伪轨跟踪性质的较为简洁的充分必要条件；最后本文借助于从可定向的闭曲面到不可定向闭曲面的复叠投射，讨论了不可定向闭曲面上的C〓-流与其提升的轨线之间的联系，解决了不可定向闭曲面上C〓-流具有伪轨跟踪性质的判定问题。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。