Artificial and natural electromagnetic structures with strongly inductive surface impedance

Artificial and natural electromagnetic structures with strongly inductive surface impedance are considered. The object of the research is layered structures of the “dielectric-conductor” type. The existence of impedance media with the maximum possible phase of a strongly inductive impedance in the range from a few hertz to tens of gigahertz has been established. The results of numerical modelling of the propagation of decimeter radio waves over a plane strongly inductive surface are presented, these numerical results are necessary for calculating the attenuation function W and the field level E of microwave electromagnetic waves.

Representing Virtual Transparent Objects on Optical See-Through Head-Mounted Displays Based on Human Vision

In this study, we propose two methods for representing virtual transparent objects convincingly on an optical see-through head-mounted display without the use of an attenuation function or shielding environmental light. The first method represents the shadows and caustics of virtual transparent objects as illusionary images. Using this illusion-based approach, shadows can be represented without blocking the luminance produced by the real environment, and caustics are represented by adding the luminance of the environment to the produced shadow. In the second method, the visual effects that occur in each individual image of a transparent object are represented as surface, refraction, and reflection images by considering human binocular movement. The visual effects produced by this method reflect the disparities among the vergence and defocus of accommodation associated with the respective images. When reproducing the disparity, each parallax image is calculated in real time using a polygon-based method, whereas when reproducing the defocus, image processing is applied to blur each image and consider the user’s gaze image. To validate these approaches, we conducted experiments to evaluate the realism of the virtual transparent objects produced by each method. The results revealed that both methods produced virtual transparent objects with improved realism.

Integral equation method for the attenuation factor calculation with consideration of the earth's surface impedance.

This paper presents a new integral equation to calculate the attenuation factor near the Earth's surface. An expression for the attenuation function computation at arbitrary heights is derived and the distance dependences of the attenuation factor are presented. The correspondence of the numerical results with analytical calculations for the planar and spherical surface is shown. The results for the real terrain profile are given.

Theoretical "t-z" Curves for Piles in Radially Inhomogeneous Soil

Accurate estimates of pile settlement are key for efficient design of axially loaded piles. Calculations of pile settlement can be simplified using one-dimensional “t-z” curves describing pile settlement at a certain depth as a function of side friction. In the realm of this simplified framework, theoretical “t-z” curves can be derived by substituting an attenuation function describing the variation of shear stress with distance from the pile, into a soil constitutive model relating shear strain to shear stress, then integrating with respect to distance to get the settlement at the pile circumference due to an applied shear stress. A handful of analytical “t-z” curves are available in the literature using the concentric cylinder model to define an attenuation function; these include solutions for linear-elastic, power-law and hyperbolic constitutive models. However, radially homogeneous soil has often been assumed, ignoring the effect of the pile installation resulting in unconservative calculations of pile settlement. This paper considers the installation of the pile, resulting in a radially variable shear modulus distribution in the surrounding soil. A radial inhomogeneity correction factor has been developed for selected constitutive models based on two simplified functions for the soil inhomogeneity, which can be applied to the previously derived “t-z” curves produced assuming radially homogeneous soil. The performance of this simplified method is investigated.

Application of Site Amplification Factors to Determine the Local Magnitude from Borehole Seismic Stations in Taiwan

<p>Since the inception of 62 borehole seismic arrays deployed by Central Weather Bureau (CWB) in Taiwan until the end of 2018, a large quantity of strong-motion records have been accumulated from frequently occurring earthquakes around Taiwan, which provide an opportunity to detect micro-seismicity. Each borehole array includes two force balance accelerometers, one at the surface and other at a depth of a few ten-to-hundred (30-492) meters, as well as one broadband seismometer is below the borehole accelerometer. In general, the background seismic noise level are lower at the downhole stations than surface stations. However, the seismograms recorded by the downhole stations are smaller than surface stations due to the near-surface site effect. In Taiwan, the local magnitude (M<sub>L</sub>) determinations use the attenuation function derived from surface stations. Therefore, the M<sub>L</sub> will be underestimated by using current attenuation function for downhole stations. In this study, we used 19079 earthquakes to investigate the site amplification at subsurface materials between downhole and surface stations. Results demonstrate the amplification factors ranging from 1.11 to 5.74, provide the site effect parameter at shallow layers and have a strong relationship with Vs30. Further, we apply the amplification factors to revise the station local magnitude for downhole station. The revised M<sub>L</sub> at downhole stations correlate well with the M<sub>L</sub> at surface stations. Implement of the downhole station in the M<sub>L</sub> determination, it enhances the ability to detect the micro-earthquake and makes the earthquake catalog more comprehensive in Taiwan.</p>