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Acoustic Cavitation
Published in Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin, Cavitation and Associated Phenomena, 2021
Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin
Equation (6.1.21) has many meanings and contains many effects, so to say. At first, we see that the volume may change with the electric field strength—this is the so-called electrostriction effect; its analogue in a magnetic field will be considered below. Also, the right-had side of the equation (6.1.21) reflects some connection between the polarization density P and pressure p. If we have to deal with the dependence P(p) in its direct, physical sense,4 i.e., suppose the change in the polarization density due to the change in pressure, then this is the manifestation of a direct piezoelectric effect. The opposite case, for the dependence p(P), when the variation in P leads to variation in pressure, corresponds to the reverse piezoelectric effect.
Organic Molecular Nonlinear Optical Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
A response of a dielectric material to an applied electric field E is described by an induced polarization density P. The medium is said to be nonlinear if the relation between the induced polarization density P and the applied field E is nonlinear. According to a simple classical theory, the charged particles in a dielectric material are bound together with bonds that have some elasticity. When the electric field is applied, electric dipole moments are induced, which oscillate with the same frequency as the applied field, when the restraining forces are harmonic. For high enough external fields, the restraining elastic forces for charged particles become nonlinear functions of the displacement, and therefore the relation between the polarization density P and the applied field E becomes nonlinear.
Electrical Field in Materials
Published in Ahmad Shahid Khan, Saurabh Kumar Mukerji, Electromagnetic Fields, 2020
Ahmad Shahid Khan, Saurabh Kumar Mukerji
The electric susceptibility of a dielectric material is a measure of its sensitivity to the polarization in the presence of an electric field E. It is denoted by a Greek letter χe (chi) and can be considered as the constant of proportionality in the relation of electric field E and the induced dielectric polarization density P. These are related as: P=εo⋅χe⋅E
Machine learning approach to transform scattering parameters to complex permittivities
Published in Journal of Microwave Power and Electromagnetic Energy, 2021
Robert Tempke, Liam Thomas, Christina Wildfire, Dushyant Shekhawat, Terence Musho
At GHz frequencies, the electromagnetic interactions are quantized by a material’s dielectric properties or the dynamics of dipole interactions. The dielectric constant of a material is the ability of the material to store electrical energy. While the loss tangent of a material is a quantification of the energy loss or dissipation of the dipole relaxation. The complex dielectric description of a material is defined as εr= ε’-iε”, where ε’ is the real portion and ε” is the imaginary portion. Here the real portion of the dielectric can be related to the polarization density, which can be conceptualized as the dipole density. The imaginary term is proportional to the dissipation or relaxation rate of the dipoles. For microwave material engineering, the characterization of a material’s dielectric is critical to understanding the response to the incident EM field. The material response of most dielectrics is non-linear and the complex dielectric properties are often change with temperature and frequency. Moreover, when dealing with heterogeneous materials such as powders, the granular structure of the materials often significantly influences the dielectric response (Bussey 1967; Zangwill 2013). One reason for the change in the response is the confinement of dipoles. However, if the spatial extend of the dipoles are on the order or less than the individual particle size, the dielectric response is comparable to the bulk material. Another reason is the granular material is a composite system composed of the dielectric grains and surrounding environment between the particles. If the dielectric properties of the environment are known, the properties of the granular material can often be determined from the mixture, but this an additional source of uncertainty. The final reason is the shape of the particles influences the response. By increasing confidence through the development of improved inverse techniques, many of these aformentioned non-linear resonses of dielectric and be better understood.