public static function getInstance()
 {
     if (self::$_instance === null) {
         self::$_instance = new self();
         self::$_instance->_table = 'user_article';
     }
     return self::$_instance;
 }
 public function unreadAction()
 {
     $this->view->article = Application_Model_UserArticleRepository::getInstance()->unread($this->getParam('id'));
 }