fix bug

app/controllers/homework_commons_controller.rb

@@ -208,7 +208,7 @@ class HomeworkCommonsController < ApplicationController
               student_work_to_xlsx(@work_excel,@homework)
               exercise_export_name = current_user.real_name + "_" + @course.name + "_" + @homework.name + "_" + Time.now.strftime('%Y%m%d_%H%M%S')
 
-              render xlsx: "#{exercise_export_name.encode('UTF-8', 'gb2312', {:invalid => :replace, :undef => :replace, :replace => ' '}).strip.first(30)}",template: "homework_commons/works_list.xlsx.axlsx",locals:
+              render xlsx: "#{exercise_export_name.encode("GBK", :invalid => :replace, :undef => :replace, :replace => " ").strip.first(30)}",template: "homework_commons/works_list.xlsx.axlsx",locals:
                   {table_columns: @work_head_cells,task_users: @work_cells_column}
             }
           end