Hello, I have lost my IPad during traveling ..how can I remove it from my account and to make sure that the person who take it is not using my account

Report to police along with serial number. Change all your passwords.

These links may be helpful.

How to Track and Report Stolen iPad

http://www.ipadastic.com/tutorials/how-to-track-and-report-stolen-ipad

Reporting a lost or stolen Apple product

http://support.apple.com/kb/ht2526

Report Stolen iPad Tips and iPad Theft Prevention

http://www.stolen-property.com/report-stolen-ipad.php

How to recover a lost or stolen iPad

http://ipadhelp.com/ipad-help/how-to-recover-a-lost-or-stolen-ipad/

How to Find a Stolen iPad

http://www.ehow.com/how_7586429_stolen-ipad.html

Apple Product Lost or Stolen

http://sites.google.com/site/appleclubfhs/support/advice-and-articles/lost-or-st olen

Oops! iForgot My New iPad On the Plane; Now What?

http://online.wsj.com/article/SB10001424052702303459004577362194012634000.html

If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.

How to Find Your iPad Serial Number

http://www.ipadastic.com/tutorials/how-to-find-your-ipad-serial-number

iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number

http://support.apple.com/kb/HT4061

 Cheers, Tom 😉

In find my iPhone app click "remoteclock"

Or remote wipe