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Because of its stable propagation characteristics and small attenuation in the medium, low-frequency (LF) electromagnetic wave can penetrate into the sea and underground with small loss. Although its transmission bandwidth is narrow, which limits its application range, it has irreplaceable wide applications in long-distance navigation, communication and frequency release, especially in underwater communication. Therefore, the study of low frequency/very low frequency (LF/VLF) propagation is of great theoretical and military value. In the LF/VLF communication systems, the transmitting antenna is an extremely important part, and its performance has an important influence on the whole system. However, the wavelength of the LF electromagnetic wave is very long. In order to obtain the ideal radiation effect, the traditional method needs a huge transmitting antenna system, which is too large in size and power consumption. Therefore, it will be a disruptive innovation in the field to realize a technology that can significantly reduce the size the existing LF/VLF information network communication system. In view of this, in this paper we propose a kind of LF/VLF signal transmitting antenna in which an excitation device is used to drive the polarization charge of the electret to move mechanically. By accelerating the charge to form a conductive alternating electromagnetic field which can generate and radiate electromagnetic wave, under the excitation of the wave source, it carries the energy and information in the form of energy flow and propagates in a certain medium. Then, through using the magnetic field receiving system to measure the magnetic field vector in the electromagnetic wave, the effective LF/VLF signal can be obtained, thus achieving the high electromagnetic wave effective radiation which overturns the restriction that the antenna size needs to be comparable to the wave length of the radiation signal in the traditional LF navigation communication system. At the same time, an analytical model of magnetic field propagation is established based on this structure, and the influence of antenna size, shape and other relevant parameters on the performance of antenna communication are studied as well. In order to reduce the loss of accuracy and improve the calculation speed, it is necessary to choose the correct analytical model and the appropriate parameters of magnetic field generated by the mechanical antenna according to the actual situation. The research work is of great significance for designing and optimizing mechanical antennas.

In this paper, back commutation phenomena far narrow slot arc quenching chamber in AC low voltage current limiting circuit breaker is investigated by both testing and theoretical methods. It is shows that as compared with iron chute chamber, narrow slot chamber reduces the back commutation phenomena in interrupting process, but causes the lower arc voltage in the condition of same chamber size. According to the above results, a new hybrid arc quenching chamber for current limiting circuit breaker which synthesized the advantages of two kinds of arc chamber is presented.

The thickness of an active layer is limited by its low mobility of carriers in a polymer solar cell composed of the blend bulk-heterojunction formed by P3HT as donor material and PCBM as acceptor material, which can affect the light absorption of the polymer solar cell. Metal nanocrystals-doped polymer active layer can enhance its inner electrical field and absorb light due to the surface plasmon resonance (SPR) effect of the nanocrystals. Two-dimensional electrical field distributions in the polymer solar cells are simulated based on finite difference time domain (FDTD) approach, under the assumption that the diameter of doping nano-Ag is 50 nm, the distance between two nanocrystals is 50nm and the incident light wavelength is 400 nm or 500 nm. The electrical field distributions over the cross-section of nano-Ag are also simulated at the incident light angle of 15°, 45°, 60°, respectively. The light absorption of different devices are calculated, in which the sizes of nano-Ag take 10 nm, 20 nm and 50 nm, respectively, Particles of nano-Ag are dispersed in PEDOT:PSS layer. Moreover, the light absorption is calculated at the incident light angles of 15°, 45°, 60°, respectively. Results show that the electrical field is redistributed due to the SPR effect caused by nano-Ag in the polymer active layer. A larger size of nano-Ag leads to light scattering in a wider angle, thus results in more light absorption by the device. Here, the colloid of nano-Ag is prepared from an organic salt of Ag, and the polymer solar cell with nano-Ag is fabricated in the structure of glass /ITO (～100 nm) /PEDOT:PSS (40 nm) /P3HT:PCBM (～100 nm)/(nano-Ag) /LiF (1 nm) /Al (120 nm). Furthermore, experimental results show that the nano-Ag doped in P3HT:PCBM layer increases light absorption and improves the electrical performance of the device, which enhances the incident photon conversion efficiency (IPCE) in spectrum at 520nm by 17.9%.