zend框架模型创建错误

我刚刚开始使用zend框架。我在zend 创建了一个项目

结构

 application
     configs
         application.ini
     layouts
     modules
         core
           DB
             Dbclass.php
           Table
         default
           controllers
           views
           forms
     bootstrap.php
 library
 public
 index 

我的引导文件包含

 public function _autoload(){
    set_include_path(
    '/application/modules/core/DB' 
    . PATH_SEPARATOR . 
    '/application/modules/core/Table' 
    . PATH_SEPARATOR . 
    get_include_path());
}
public function _init(){
    $front = Zend_Controller_Front::getInstance();
    $front->setControllerDirectory(array(
    'default' => APPLICATION_PATH.'/modules/default/controllers'
    ));
}

我的application.ini文件包含

 [production]
 phpSettings.display_startup_errors = 0
 phpSettings.display_errors = 0
 phpSettings.date.timezone = "Europe/London"
 ;includePaths.library = APPLICATION_PATH "/../library"
 bootstrap.path = APPLICATION_PATH "/Bootstrap.php"
 bootstrap.class = "Bootstrap"
 appnamespace = "Application"
 ;resources.frontController.controllerDirectory = APPLICATION_PATH "/controllers"
 resources.frontController.moduleDirectory = APPLICATION_PATH "/modules"
 resources.frontController.moduleControllerDirectory = APPLICATION_PATH   "/modules/controllers"
resources.frontController.defaultModule = "default"
resources.frontController.moduleDirectory = APPLICATION_PATH "/modules"
resources.frontController.params.displayExceptions = 0

当我在indexcontroller 中创建对象时

 $new_object = new Dbclass();

有一个错误显示

 Fatal error: Class 'Dbclass' not found in D:'xampp'htdocs'pubman'application'modules'default'controllers'IndexController.php on line 16

如果有人知道这一点，请帮帮我。

提前谢谢。