some过去分词是什么

该词没有过去分词，例如：

1、There have been some problems but basically it's a good system.虽然出现过一些问题，但这基本上仍不失为一个好系统。

2、There are some obvious practical applications of the research.这项研究有一些明显的实际用途。

3、I had some idea of what the job would be like.我对于这份工作有了一些了解。