Microscale magnetoelectricity: Effect of particles geometry, distribution, and volume fraction

Achieving efficient magnetoelectric coupling of core-shell and particulate multiferroic composites has been a challenging hurdle; however, research has shown unwavering interest to overcome this barrier in pursuit of their implementation into promising potential applications. Herein, a fully coupled computational model of core-shell and particulate composites is developed and verified to investigate the magnetoelectric interactions of the particle and matrix on the microscale. The effects of particle geometry, settling, and agglomeration were exhaustively studied by investigating seven different shapes and a wide range of vertical and lateral particle spacing. Overall, it was found that utilizing particle geometries and positioning that closely resemble a laminate configuration, such as a prolate ellipsoid and horizontal particle alignment, enhances the magnetoelectric coupling of the composite structure. The results coincided with the experimental results concerning settling and agglomeration.

Pattern interaction effect

Unexpected responses of physical systems to external stimuli can be observed when the stimuli are organized into spatial patterns and, especially, when stimuli of different physical origins are involved, leading to the pattern interaction problem. Combinations of weak stimuli—individually only capable of producing marginal local responses—can produce a global response without involving any bifurcations. Its existence is demonstrated by the interaction of properly tuned topography and temperature patterns. When these patterns overlap in a symmetry preserving manner, the resulting convection has the form of local rolls. When these patterns are misaligned, the resulting convection involves global horizontal particle movement with direction depending on the type of misalignment.

Tsunami-generated magnetic fields have primary and secondary arrivals like seismic waves

A seafloor geomagnetic observatory in the northwest Pacific has provided very long vector geomagnetic time-series. It was found that the time-series include significant magnetic signals generated by a few giant tsunami events including the 2011 Tohoku Tsunami. Here we report that the tsunami-generated magnetic fields consist of the weak but first arriving field, and the strong but second arriving field—similar to the P- and S-waves in seismology. The latter field is a result of coupling between horizontal particle motions of the conductive seawater and the vertical component of the background geomagnetic main field, which have been studied well so far. On the other hand, the former field stems from coupling between vertical particle motions and the horizontal component of the geomagnetic main field parallel to tsunami propagation direction. The former field has been paid less attention because horizontal particle motions are dominant in the Earth’s oceans. It, however, was shown that not only the latter but also the former field is significant especially around the magnetic equator where the vertical component of the background magnetic field vanishes. This implies that global tsunami early warning using tsunami-generated magnetic fields is possible even in the absence of the background vertical geomagnetic component.

Tunable interactions between particles in conically rotating electric fields

Tunable interactions between colloidal particles in external conically rotating electric fields are calculated, while the (vertical) axis of the field rotation is normal to the (horizontal) particle motion plane.

Vector Ocean Ambient Noise Spectrum Simulation Based on Parabolic Equation Model in Shallow Water

Ocean ambient noise spectrum is one of the most important characteristics of ambient noise. An ocean vector ambient noise field model was built up based on parabolic equation in this paper. Then the spectra of sound pressure, horizontal particle velocity and vertical particle velocity were calculated applying the model considering noise sources well distributed on the surface with typical summer sound speed profile in South China Sea. The simulation results showed that spectra of sound pressure, horizontal particle velocity and vertical particle velocity were obviously not varied with depth. Then, the simulated results were compared with the experiment results at the receiving depth of a trail in South China Sea in July 2012. Compared with the experimental results, the simulation results are consistent well with the experimental one of sound pressure and horizontal particle velocity in the trend. But the simulation values at low frequency band below 500[Formula: see text]Hz, are not consistent with the experimental one very well, in the band the simulation results are lower than the experimental by about 3–5[Formula: see text]dB. But the simulation result of vertical particle velocity was not consistent with the experimental one, illustrating that the precision of the model might not be enough in the vertical direction.