Study of Geoprocesses with Complementary Mechanical and Electromagnetic Wave Measurements in an Oedometer

Evaluation of particulate materials using wave-based techniques

For clarifying the excitation mechanism of co-seismic electromagnetic (EM) waves, I have been observing earthquake-related EM waves in the deep earth and above the ground together with measurements of seismic waves, and also conducted a laboratory experiment. As the result, I have found that EM waves were easily excited by seismic P-wave oscillations in the earth's crust due to piezo-electric effect. The amplitude of the EM wave was enlarged at arrival of seismic S-wave which largely deformed the P-wave amplitude. It has been confirmed, from observed waveforms, that a large amplitude of co-seismic EM wave always appears in the wave-front of the seismic S-wave. Since the EM wave was radiated but rapidly decayed due to a large electrical conductivity of the earth's crust, we could imagine a composite wave system, in which a rapidly decaying co-seismic EM wave is antecedent to the seismic S-wave, and the system is moving with the velocity of the seismic S-wave. It has been also confirmed that a co-seismic EM wave detected above the ground showed ellipsoidal polarization although another EM wave simultaneously detected in the earth showed a linear polarization, which is a result of phase shifts of the EM wave in its penetration through a boundary of two media (from the earth medium to the air).

Mechanical and electromagnetic waves are commonly used in nondestructive testing (NDT) techniques for evaluating the materials and structures in civil engineering industry, due to their good examination of defects inside the matter. However, the individual use of mechanical wave or electromagnetic wave in NDT methods sometimes does not fulfill the satisfactory detection in practice because of the operational inconvenience and low sensitivity. It has been demonstrated that the combination of using both types of waves can achieve a better performance for NDT application and would be the future direction for defect detection, as the advantages of each physical wave are picked out whereas the weaknesses are mitigated. This paper discusses the fundamental mechanisms and the current applications of using mechanical and electromagnetic waves for defect detection, with the goal of providing the physical knowledge and the perspectives of developing the NDT applications with these two types of waves. Typical mechanical-wave-based NDT methods such as acoustic emission, ultrasonic technique, and impact-echo method are reviewed. In addition, NDT methods using electromagnetic wave, which include optical fiber sensing technique, laser speckle interferometry and laser reflection technique are discussed. Advantages and disadvantages of these methods are outlined. In particular, we focus on a recent NDT method called acoustic-laser technique, which utilizes both the mechanical and electromagnetic waves. The basic principles and some important experimental data recorded by the acoustic-laser technique are described and its future development in the field of defect detection in civil infrastructure is presented.

Analytic expressions are obtained for the energy fl ux and density of refracted nonuniform waves produced during total refl ection at the boundary between two isotropic media for the general case of elliptically polarized incident light. The average values are determined as functions of the parameters of the adjoining media and the angle of incidence. The cases of linearly and circularly polarized incident waves are examined in detail. An explicit general expression relating the energy fl ux and density of these waves for arbitrarily polarized incident light is obtained. Introduction. Nonuniform waves are damped (or amplifi ed in the case of inversion media) plane electromagnetic waves for which the planes of equal phase and equal amplitude are not parallel to one another (1). These waves arise in transparent media during total internal refl ection of light and in absorbing (amplifying) media for obliquely incident light. The properties of nonuniform waves are important in a number of cases of practical importance, such as in studies of the propagation of electromagnetic waves in light guides (waveguides), whose operation is based on the phenomenon of total internal refl ection. Nonuniform electromagnetic waves are characterized by the fact that their polarization curves for the vectors E and H can be different, i.e., E and H have different polarizations (1). It is also important to note that the phase velocity of these waves in a medium depends on the angle of incidence. Studies of nonuniform waves at the interfaces of dielectric media have recently attracted special interest in connection with their possible use in high-effi ciency thin-fi lm polarization beam splitters, as well as in optical fi lters and antirefl ection coatings with a large numerical aperture and spectral width (1-4). Another important area in research on nonuniform waves is related to the development of so-called all-angle refl ectors (5). Extending the capabilities and improving the characteristics of devices of this kind will require studies of the features of nonuniform waves under general conditions of elliptical (including the special case of circular polarization), and not just linear, polarization. Although the general theory of nonuniform electromagnetic waves was developed back in the 1960's, research on the behavior of these waves at the interfaces of different media has not lost its importance. Thus, knowledge of the properties and behavior of nonuniform electromagnetic waves at the interfaces of media, in particular their energy characteristics, is of practical, as well as theoretical, interest. This paper is a study of the energy fl ux and density of nonuniform refracted waves which arise under the conditions of total internal refl ection at the interface of two isotropic media as functions of the parameters of the adjoining media and the angle of incidence for the general case of polarized incident radiation. In particular, explicit analytic expressions for their average values in the case of a linearly polarized wave with an arbitrary oscillation azimuth, as well as in the case of circularly polarized incident radiation. To establish the dependence of the energy fl ux and density of a nonuniform wave on the parameters of the adjoining media and the angle of incidence, we begin with the solutions of the corresponding boundary problem for Maxwell's equations. We write the electric fi eld vectors of incident (E1), refl ected ( c 1 E ), and transmitted (E2) plane waves with a harmonic time dependence (~e -i�& t ) in the form

Metamaterials are artificially structured composite media with a unique electromagnetic (EM) response that is absent from naturally occurring materials, which appears counterintuitive and aggravates traditional difficulties in perceiving the behavior of EM waves. The aim of this study was to better understand the interaction of EM waves with metamaterials by virtual visualizing the accompanying physical phenomena. Over the years, virtual visualization of EM wave interactions with metamaterials has proven to be a powerful tool for explaining many phenomena that occur in metamaterials. In this study, we performed virtual visualization of the interaction of an EM plane wave with a split-ring resonator (SRR) metamaterial structure, employing CST Studio software for modeling and comprehensive simulations of high-frequency EM fields of 3D objects. The SRR structure was designed to have its magnetic resonance at the frequency f = 23.69 GHz, which is of interest for antennas supporting wireless microwave point-to-point communication systems (e.g., in satellite systems). Our numerical calculations of the coefficients of absorption, reflection, and transmission of the EM plane wave incident on the SRR structure showed that the SRR structure totally reflected the plane EM wave at the magnetic resonance frequency. Therefore, we focused our research on checking whether the results of numerical calculations could be confirmed by visualizing the total reflection phenomenon on the SRR structure. The performed vector-field visualization resulted in 2D vector maps of the electric and magnetic fields around the SRR structure during the wave period, which demonstrated the existence of characteristic features of the total reflection phenomenon when the EM plane interacted with the studied SRR, i.e., no EM field behind the SRR structure and the standing electric and magnetic waves before the SRR structure, thus, confirming the numerical calculations visually. For deeper understanding the interaction of the EM plane wave with the SRR structure of reflection characteristics at the magnetic resonance frequency f = 23.69 GH, we also visualized the SRR structure response at the frequency f = 21 GHz, i.e., at the so-called detuned frequency. As expected, at the detuned frequency, the SRR structure lost its metamaterial properties and the obtained 2D vector maps of the electric and magnetic fields around the SRR structure during the wave period showed the transmitted EM wave behind the SRR structure and no EM (fully) standing waves before the SRR structure. The visualizations presented in this study are both unique educational presentations to help understand the interaction of EM plane waves with the SRR structure of reflection characteristics at the magnetic resonance and detuned frequencies.

This paper documents a study of concentration diffusion with complementary mechanical and electromagnetic wave measurements. The paper starts with a review of the fundamentals of interparticle forces and wave–geomedia interaction. Experimental data were collected during the diffusion of a high-concentration solution of potassium chloride through different soils with different boundary conditions. Bentonite and kaolinite contracted during diffusion. The interaction between the concentration gradient, true interparticle forces, and fabric changes produced a pore-water pressure front that advanced ahead of the concentration front. The complex permittivity changed with the advance of the concentration front, reflecting the decrease in moisture content and the increase in conductivity. Concentration diffusion affected shear wave propagation through changes in true interparticle forces. Bentonite showed a significant increase in shear wave velocity, whereas the velocity of propagation in kaolinite decreased. Published differences in the behavior of bentonite and kaolinite were compiled and hypotheses are proposed to explain observed phenomena. Key words : mechanical waves, electromagnetic waves, clays, diffusion, double layer.

We detected electromagnetic (EM) waves directly excited by earthquakes in a deep borehole and confirmed them by simultaneous capturing of their waveforms and of seismic waves measured at the same observation site. Furthermore, the excitation mechanism of the EM pulse was confirmed as the piezoelectric effect by a laboratory experiment, in which a seismic P-wave was readily generated by a small stress impact, and the EM wave was simultaneously excited basically by the P-wave. Here, we show behaviors of seismic waves and of their excited EM waves when small and large earthquakes occurred. We also found that EM waves excited by seismic waves have leaked out of the ground surface.

The use of expert systems to determine pavement fatigue life (such as backcalculation) is strongly constrained by empirical assumptions. An important obstacle for the development of this research area is a conflict between the complexity of pavement model and actual limitations of methods used to identify its parameters. This article describes the original concept of device, which combines advantages of different methods of testing the pavement needed to calculate its fatigue life. Combined methods are based on the theory of propagation of both mechanical waves and electromagnetic waves in the layered pavement medium. The proposed hybrid solution is the starting point for the development of an expert system based on semi-invasive and non-invasive methods of obtaining the calculation values for parameters of pavement layers. It is believed that backcalculation results based on such identification are characterized by lower uncertainty comparing to the standard approach. As a consequence, the precision of overlay design for pavements will be increased.

Effect of interconvertibility of electromagnetic and gravitational waves in strong external electromagnetic fields and the propagation of waves in the field of a charged “black hole”: PMM vol. 38, n≗ 6, 1974, pp. 1122–1129

Recent progress on hybrid fibrous electromagnetic shields: Key protectors of living species against electromagnetic radiation

Soil properties from seismic intrinsic dispersion

Breast cancer is the most common cancer in women, and non-destructive detection of the tumor is vital. The interaction of electromagnetic waves with breast tissue and the behavior of waves after interaction are used to model tumor detection mathematically. The behavior of electromagnetic waves in a medium is described using Maxwell's equations. Electromagnetic waves propagate according to the electrical properties of a medium. Since the electrical properties of tumor tissue are different from those of normal breast tissue, it is assumed that the tumor is a lossy dielectric sphere, and the breast is a lossy dielectric medium. Under this assumption, Maxwell's equations are used to calculate the scattered field from the tumor. The field scattered by the tumor is different from other tissues because their dielectric properties are different. The location and size of the tumor can be determined by utilizing the difference in scattering from the tissues. While the scattering field from the tumor in spherical geometric form is analytically calculated, it is not analytically possible to calculate the scattering field from the tumor in different geometric shapes. In addition to non-destructive detection of the tumor, an efficient numerical method, the finite difference time domain method (FDTD), is used to simulate the field distribution. After the location of the tumor is determined, the Alternating Direction Implicit (ADI) FDTD method, which gives simulation results by dividing the computation domain into smaller sub-intervals, can be used. Scattered fields are calculated analytically in the geometry where the tumor is in the form of a smooth sphere, and in more complex geometry, the field distributions are successfully obtained with the help of MATLAB using FDTD and ADI-FDTD algorithms.

This chapter is the first of three that deal in detail with the wave equation for three different types of waves. Mechanical waves are described in this chapter, Chapter 5 discusses electromagnetic waves, and Chapter 6 is all about quantum-mechanical waves. You'll find frequent reference in these three chapters to concepts and equations contained in Chapters 1, 2, and 3, so if you've skipped those chapters but find yourself needing a bit more explanation of a particular idea, you can probably find it in one of the earlier chapters. The layout of this chapter is straightforward. After an overview of the properties of mechanical waves in Section 4.1, you'll find a discussion of two types of mechanical waves: transverse waves on a string (Section 4.2) and longitudinal pressure waves (Section 4.3). Section 4.4 is about energy and power in mechanical waves, and Section 4.5 discusses the reflection and transmission of mechanical waves. Properties of mechanical waves We're surrounded by the electromagnetic waves of Chapter 5, and we're made of particles that can be described by the quantum-mechanical waves of Chapter 6, but when you ask most people to describe a wave, they think of the mechanical waves that are the subject of this chapter. That's probably because the “waving” of many types of mechanical waves can be readily observed. For mechanical waves, the waving is done by bits of mass – atoms, molecules, or connected sets of particles, which means that mechanical waves can exist only within a physical material (called the “medium” in which the wave propagates). For mechanical waves such as a wave on a string, the disturbance of the wave is the physical displacement of matter from the undisturbed (equilibrium) position. In that case, the disturbance has dimensions of distance, and the SI units of the disturbance are meters. In other mechanical waves, such as pressure waves, you may encounter other measures of the wave's disturbance. For example, in sound waves, the disturbance may be measured as the change in the density of the medium or the change in the pressure within the medium from their equilibrium values.

How things work: the physics of everyday life

The propagation of coupled mechanical and electromagnetic waves in a conducting elastic medium when the entire system is in an external magnetic field is considered. We use the mathematical model introduced by Dunkin and Eringen in 1963. The influence of an external magnetic field and medium parameters on the dispersion and attenuation of coupled electromagnetic and elastic waves is analyzed. We also simulated the propagation of coupled mechanical and electromagnetic waves in layered media using the Ursin method with a weak/strong external magnetic field. The results confirmed the effectiveness of using Ursin’s method in modeling magnetoelastic oscillations and can be used to analyze electrodynamic phenomena accompanying disturbances of the geomagnetic field during the movement of the conducting layers of the Earth.