Question: How do I change the networks edges and vertex sytle?

I just use the Maple for one month, I want to use the Graph theory Draw a graph(networks) with 70 vertex, but the arrow of edges is always near  the beging point of 

arc, which lead to the arrow can't  be seen clearly, I want to change the sytle of edges by changing the arrow position , but I don't find a correct method , can anyone help me ? Thank you very much!  

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