关系代词省略后，动词用ing形式，还是保持原来形式？

例如:
This organization also closely monitors economic development projects which receive assistance to ensure the success of the investment.

省略which之后：This organization also closely monitors economic development projects receiving assistance to ensure the success of the investment.

是不是关系代词省略之后，原来的动词要改为动名词形式？有没有一些情况不用变的？
一般这些从句的省略形式，省略前后句子的结构或一些词语的形式一般会发生什么变化？
最近在备考托业，PART5.6的词汇语法搞得糊涂了。
先谢过各位大神！

which receive assistance to ensure the success of the investment.----receiving assistance to ensure the success of the investment.

这是现在分词不是动名词

不是省略，是转换

定从转换成非谓语动词有三种形式：ving，ved，to v

he is the man who helps me a lot----he is the man helping me a lot

he is the man who is fired by the boss---he is the man  fired by the boss

this is the first time that i went to beijing---this is the first time  to go to beijing