Zend Framework , Model Class not found in Module-Collection of common programming errors

I’ve Created an application with these details :

1- zf create project MyApp

2- zf create module admin

3- zf create controller Index 1 admin

MyApp/application/modules/admin/controllers/IndexController.php :

class admin_IndexController extends Zend_Controller_Action
{

    public function init()
    {
        error_reporting(E_ALL);
        ini_set('display_errors', 'On');
    }

    public function indexAction()
    {

        $aa = new Admin_Model_DbTable_Posts();

    }

}

application.ini :

[production]
phpSettings.display_startup_errors = 0
phpSettings.display_errors = 0 
includePaths.library = APPLICATION_PATH "/../library" 
bootstrap.path = APPLICATION_PATH "/Bootstrap.php"
bootstrap.class = "Bootstrap" 
appnamespace = "Application"
resources.frontController.controllerDirectory = APPLICATION_PATH "/controllers"
resources.frontController.params.displayExceptions = 0
resources.frontController.moduleDirectory = APPLICATION_PATH "/modules"

MyApp/application/modules/admin/models/DbTable/Posts.php :

class Admin_Model_DbTable_Posts extends Zend_Db_Table_Abstract    
{
    public function init()
    {

    }
}

In this point I get the error :

Fatal error: Class 'Admin_Model_DbTable_Posts' not found in /var/www/MyApp/application/modules/admin/controllers/IndexController.php on line 16

and When i put this line on application.ini

resources.modules[] =

And add bootstratp.php in admin folder with these content

class Admin_Bootstrap extends Zend_Application_Bootstrap_Bootstrap
{

}

After a long period of requesting , i get this error :

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

what should i do to make it work?