content_image/365049.jpg content_image/365052.jpg content_image/365057.jpg content_image/365058.jpg content_image/365050.jpg content_image/365051.jpg
<img src='content_image/365049.jpg'>

<img src='content_image/365052.jpg'>

Therefore, by virtue of the first equation of Eq. (2.3) we have 

We finally write down the following approximate relation obtained numerically: 

<img src='content_image/365057.jpg'>

<img src='content_image/365058.jpg'>

<img src='content_image/365050.jpg'>

<img src='content_image/365051.jpg'>

