Regional-scale continental magnetotelluric (MT) programs such as AusLAMP are naturally bounded by the continental shelf and electrically-conducting seawater. Within a few hundred kilometres of the ...coastline, long-period MT data may be strongly influenced by induction in the seawater, a phenomenon known as the coast-effect. Thus, 3D inversion of gridded long-period MT data for continental lithosphere models requires good constraints on the resistivity of the seawater, oceanic crust and upper mantle, and into the asthenosphere.
In this paper, we discuss the concept of a horizontal adjustment distance. This is the horizontal distance away from a major contrast in electrical conductance at which the anomalous electric fields are attenuated by a factor of 1/e from a 1D response, and is somewhat analogous to the more widely-known skin-depth concept. For seafloor MT, this adjustment distance can be thousands of kilometres. Inland, the effect depends on the conductance of the sedimentary cover, and the depth-integrated resistivity of the upper crust, and can vary from a few kilometres to hundreds of kilometres. We discuss the implications in terms of 3D smooth inversion that inherently minimises gradients in subsurface resistivity and suggest that the coast effect may be significantly underestimated in some continental models.
The study describes the characteristic of field seedling vacuum-vibration tray precision seeder, discuses the necessity for horizontal adjustment on the precision seeder. Horizontal adjustment ...parallel mechanism is designed, DOF and characteristics of parallel mechanism’s moving platform are systematically analysized, proved the mechanism can meet the horizontal adjustment of two-level tilt angle,which provided a theoretical basis for horizontal adjustment of the seeder.
Dust storms are significant meteorological phenomena which attenuates signal level especially at Ku band and higher frequencies with direct impact on telecommunications system performance. Few ...prediction models have been developed to calculate the attenuation due to dust storm in dB/km. All prediction models have assumed that the intensity of dust storm is uniformly distributed around the area covered by the dust storm. It has been found that the dust storm intensity is not uniformly distributed along the horizontal path. However, to predict the total attenuation due to dust storm that a microwave link might suffer, an adjustment factor is needed to account for the variation of dust storm intensity along the propagation path. In this paper an adjustment factor which reflects the variation of dust storm horizontally (terrestrial links) has been derived based on the analysis of the horizontal dust storm behavior. It has been found that the estimated attenuation with the horizontal adjustment factor is very close to the measured attenuation than without using the horizontal adjustment factor.
PDF
