  function _canTransfer(address from,uint256 _amount) private returns (bool) {
    if(now < beginTime){
      return false;
    }
    if((balanceOf(from))<=0){
      return false;
    }
    releaseToken(from);
    Account memory _account = accountMapping[from];
    if(_account.ownAmount == 0){
      return true;
    }
    if(balanceOf(from).sub(_amount) < _account.ownAmount.sub(_account.releasedAmount)){
      return false;
    }
    return true;
  }