Narrow Results

The electronic conductance characteristics of a pentacene molecular tap has been investigated theoretically by a Green's function approach based on an empirical tight-binding theory in which only one π orbital electron per carbon atom is considered. The quantum transmission probability for electrons through the pentacene tap from an input to three other outputs is obtained. A strong dependence of the transmission probability on the incident electron energy and the molecular energy levels is evident for all three input–output combinations. The electronic current distributions inside the pentacene tap are calculated by a current density method based on the Fisher–Lee formula for two electron energies (E = ± 0.68 and ±1.31 eV) at which the transmission spectra peaks. The current distributions are in good agreement with the Kirchhoff quantum current momentum conservation law.

Corrosion studies on dissimilar metal joint by underwater welding are carried out in seawater by wire beam electrode method (WBE). Current and potential distributions show that the weld material and heat affected zone (HAZ) are cathodes and the base metal (BM) is anode during the first immersion. After a period of immersion in seawater, anodic current appears in the HAZ. The anodic current maintains till the end of the test. This result demonstrates that corrosion attack occurs predominantly at the HAZ after a long term immersion in seawater. The mechanism is discussed and IR drop in the rust is believed to be one of the main reasons.

In order to study the leakage magnetic field, the current and short-circuit force distribution of windings for the special transformer, firstly, the three dimensional leakage magnetic field calculation model and the corresponding equivalent circuit are established by taking advantage of field-circuit coupled method (FCCM). Then, the leakage magnetic field, short-circuit impedance and branches current distribution of low voltage winding are analyzed and verified. Finally, on the basis of the winding current distribution rule summarized by above analysis, the leakage magnetic field distribution and mechanical forces are obtained by using simplified calculation model and FEM analysis software. The verification of the magnetic field distribution and impedance ensure the reasonability of the calculation method. Therefore, this paper provides engineering practical and efficient calculation approach of parameters design for special transformer.