/**
  * Método para calcular resistencia
  *
  * @return Retorna un objeto ResistanceReactance que almacena el valor de la resistencia.
  */
 private ResistanceReactance calculate_resistance(
     TypeOfBranchCircuitInArea typeOfBranchCircuitInArea) {
   if (typeOfBranchCircuitInArea == TypeOfBranchCircuitInArea.NEUTRAL) {
     return MethodsForCalculationsGlobal.calculate_resistance(
         (Material) viewMainFeeder.getCmbMaterial().getSelectedItem(),
         (Caliber) viewMainFeeder.getCmbCalibersNeutral().getSelectedItem(),
         (Duct) viewMainFeeder.getCmbDuct().getSelectedItem());
   } else {
     return MethodsForCalculationsGlobal.calculate_resistance(
         (Material) viewMainFeeder.getCmbMaterial().getSelectedItem(),
         (Caliber) viewMainFeeder.getCmbCaliber().getSelectedItem(),
         (Duct) viewMainFeeder.getCmbDuct().getSelectedItem());
   }
 } // Fin del método
 /** Método para llenar los combos con Ductos. */
 public void fill_combos_ducts() {
   ductsFound = ServiceDuct.find_ducts();
   if (ductsFound != null) {
     for (Duct duct : ductsFound) {
       viewMainFeeder.getCmbDuct().addItem(duct);
     }
     viewMainFeeder.getCmbDuct().setSelectedIndex(0);
   } else {
     MessagesStructure.Warning(
         MessagesStructure.format(
             200, messages.getProperty(Messages.DUCTS_NO_FOUND), MessagesStructure.justify));
     viewMainFeeder.dispose();
   }
 } // Fin del método