Delete duplicate entries from a 2 dimensional array in ror

I am trying to loop an array like this..

    @mem = []
    @tran = Transport.find_all_by_month_and_vehicle(date,vehicle)
    tran.each do |t|
      @mem << [Student.find_by_id(t.mem_id), t.transport_date,
vehicle.no] if t.mem_type=="Student"
      @mem << [Employee.find_by_id(t.mem_id), t.transport_date,
vehicle.no] if t.mem_type=="Employee"
    end

And in the view page I am looping it and displaying it like this

    @mem.each do |m|
      <tr>
                <td><%= link_to m[0].first_name} %></td>
                <td > <%= m[0].age %></td>
                <td id="date"> m[1] </td>
                <td id="vehicle"> m[2] </td>
      </tr>
    <%end%>

But I am getting duplicates entries here..I need to remove duplicate
entries from this.. How do I do it?? Kindly help