Javascript AngularJS:ng模型未在UI中更新

嗨，我的UI里有日历

     <select id="selectDuration" name="selectDuration" required ui-
     select2="select2DurationSettings" ng-model="duration" ng-
     change="loadSensoryEvents()">

---

我正在更新此$scope.duration值，但此值在我的UI中未得到更新。

在控制器中使用对象并声明对象

$scope.selected = {};

HTML

<select id="selectDuration" name="selectDuration" required ui-
 select2="select2DurationSettings" ng-model="selected.duration" ng-
change="loadSensoryEvents()">

---

在控制器中使用对象并声明对象

$scope.selected = {};

HTML

<select id="selectDuration" name="selectDuration" required ui-
 select2="select2DurationSettings" ng-model="selected.duration" ng-
change="loadSensoryEvents()">