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In this investigation, Cu-Ni alloys for possible fixed dental prostheses (FDPs), with different aluminum additions were produced using vacuum atmosphere. Annealed alloys (He atmosphere) with low aluminum concentration showed a coarse dendritic structure, while samples with high aluminum concentration showed a refined dendritic structure. Structural defects analyses have shown a relative low vacancy concentrations. Hardness value increases approximately five times for the alloyed samples compared with the as-cast and unalloyed samples. Compression test results have shown a noticeable strengthening improvement, mainly in samples heat treated with 10 at % Al, while samples with 5 at % Al presented also acceptable resistance. Results are discussed in terms of dislocation mobility and hardening precipitation mechanism.

Electric power transfer maneuvers carried out in the streets of Mexico through medium voltage distribution circuits necessarily imply the interruption of service to users, even though the supplier has several operating procedures to maintain continuity of service.

This article shows the analysis for load transfer without interruption between two 23 kV distribution feeders. This procedure is not common in this type of system and requires paying primary attention to the characteristics of the electrical network for its application. The distribution circuits discussed here have their own power substation with different voltage levels. The information obtained from a state estimator, the contingency conditions, the electrical parameters of impedances and network configuration allow to carry out the simulation of the load transfer with the Alternative Transients Program software. From the simulation it is shown that load transfer without interruption is possible as long as certain operating conditions are met in the power and distribution networks. The dependence of the transfer on the voltage levels, angular phase shift of voltages and strength of the electrical network is shown, represented by its thevenin impedance at the interconnection point. The results found from the simulation indicate that the success of the interconnection is mainly a function of the electrical strength of the power substations and the phase sequence of the power transformer at the load transfer point. Certain percentages of variation of voltage and currents of the feeders are defined that must not be exceeded. The operational aspects proposed here serve as a basis to have a general interconnection procedure between distribution feeders where special attention is required in the continuity of the service due to the high expectation in the satisfaction of the user of the electrical network. Keywords: feeder, state estimator, medium voltage, power system, load transferring.

Conventional absorption and refrigeration systems use a LiBr/H2O mixture, which causes corrosion problems to the metallic components. In order to avoid this and some other problems such as crystallization and vapor pressure, some additives such as CaCl2 and/or LiNO3 are added to the LiBr/H2O mixture. In the present work, the corrosion behavior of 1018 carbon steel as well as of type 304 and 316L stainless steels was evaluated in LiBr/H2O at 80 °C with the addition of CaCl2, LiNO3, and CaCl2+LiNO3. Potentiodynamic polarization curves and electrochemical impedance spectroscopy were used for this purpose. The results showed that the corrosion current density values of all tested steels decreased with the addition of CaCl2 and/or LiNO3, which induced the formation of a passive film on carbon steel. Both types of stainless steels showed a passive film in all tested conditions, but the passive current density was the lowest, whereas the passive zone was the widest, for 316L steel. The corrosion mechanism remained unaltered for both stainless steels but was changed with the addition of CaCl2 and/or LiNO3 for carbon steel.