Inácio, S., D. Inácio, J. M. Pina, Stanimir Valtchev, M. V. Neves, and A. L. Rodrigues. "
An electrical gearbox by means of pole variation for induction and superconducting disc motor."
Journal of Physics: Conference Series. 97 (2008): 012221.
AbstractIn this paper, a poly-phase disc motor innovative feeding and control strategy, based on a variable poles approach, and its application to a HTS disc motor, are presented. The stator windings may be electronically commutated to implement a 2, 4, 6 or 8 poles winding, thus changing the motor's torque?speed characteristics. The motor may be a conventional induction motor with a conductive disc rotor, or a new HTS disc motor, with conventional copper windings at its two iron semi-stators, and a HTS disc as a rotor. The conventional induction motor's operation principle is related with the induced electromotive forces in the conductive rotor. Its behaviour, characteristics (namely their torque?speed characteristics for different number of pole pairs) and modelling through Steinmetz and others theories are well known. The operation principle of the motor with HTS rotor, however, is rather different and is related with vortices' dynamics and pinning characteristics; this is a much more complex process than induction, and its modelling is quite complicated. In this paper, the operation was simulated through finite-elements commercial software, whereas superconductivity was simulated by the E-J power law. The Electromechanical performances of both motors where computed and are presented and compared. Considerations about the systems overall efficiency, including cryogenics, are also discussed.
Lanca, M. C., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, and J. Marat-Mendes. "
Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite."
Advanced Materials Forum Iv. Eds. AT Marques, AF Silva, APM Baptista, C. Sa, FJLA Alves, LF Malheiros, and M. Vieira. Vol. 587-588. Materials Science Forum, 587-588. 2008. 613-617.
AbstractLately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.
Lanca, M. C., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, and J. Marat-Mendes. "
Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite."
Advanced Materials Forum Iv. 587-588 (2008): 613-617.
AbstractLately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.
Lanca, Carmo M., Stefan Peuckert, Eugen R. Neagu, Luis Gil, Paulo C. Silva, and Jose Marat-Mendes. "
Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite."
Advanced Materials Forum Iv. Eds. AT Marques, AF Silva, APM Baptista, C. Sa, FJLA Alves, LF Malheiros, and M. Vieira. Vol. 587-588. Materials Science Forum, 587-588. 2008. 613-617.
AbstractLately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.
Lanca, Carmo M., Stefan Peuckert, Eugen R. Neagu, Luis Gil, Paulo C. Silva, Jose Marat-Mendes, AT Marques, AF Silva, APM Baptista, C. Sa, FJLA Alves, LF Malheiros, and M. Vieira. "
Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite."
Advanced Materials Forum Iv. Vol. 587-588. 2008. 613-617.
Abstractn/a
Dell'acqua, S., S. R. Pauleta, E. Monzani, AS Pereira, L. Casella, JJG Moura, and I. Moura. "
Electron transfer complex between nitrous oxide reductase and cytochrome c(552) from Pseudomonas nautica: Kinetic, nuclear magnetic resonance, and docking studies."
Biochemistry. 47 (2008): 10852-10862.
AbstractThe multicopper enzyme nitrous oxide reductase (N2OR) catalyzes the final step of denitrification, the two-electron reduction of N2O to N-2. This enzyme is a functional homodimer containing two different multicopper sites: CuA and CuZ. CuA is a binuclear copper site that transfers electrons to the tetranuclear copper sulfide CuZ, the catalytic site. In this study, Pseudomonas nautica cytochrome C-552 was identified as the physiological electron donor. The kinetic data show differences when physiological and artificial electron donors are compared [cytochrome vs methylviologen (MV)]. In the presence of cytochrome c(552), the reaction rate is dependent on the ET reaction and independent of the N2O concentration. With MV, electron donation is faster than substrate reduction. From the study of cytochrome c(552) concentration dependence, we estimate the following kinetic parameters: K-mc512 = 50.2 +/- 9.0 mu M and V-maxc551 1.8 +/- 10.6 units/mg. The N2O concentration dependence indicates a K-mN2O of 14.0 +/- 2.9 mu M using MV as the electron donor. The pH effect on the kinetic parameters is different when MV or cytochrome c(552) is used as the electron donor (pK(a) = 6.6 or 8.3, respectively). The kinetic study also revealed the hydrophobic nature of the interaction, and direct electron transfer studies showed that CuA is the center that receives electrons from the physiological electron donor. The formation of the electron transfer complex was observed by H-1 NMR protein-protein titrations and was modeled with a molecular docking program (BiGGER). The proposed docked complexes corroborated the ET studies giving a large number of solutions in which cytochrome c(552) is placed near a hydrophobic patch located around the CuA center.