In the field of frequency-domain electromagnetic detection, skin depth is an important parameter for electromagnetic data interpretation and imaging. The classic skin depth formula is calculated based only on conductivity; the induced-polarization effect in real earth is not considered, so the imaging results have obvious errors. To solve these problems, based on plane wave theory and the Cole–Cole conductivity model, a generalized skin depth formula of polarized media is derived in the frequency domain. The accuracy of the generalized skin depth is verified through comparison with the classical skin depth. To show the practicability of this study, the theoretical data with induced polarization (IP) effects are used to explain the generalized skin depth for polarized porous media. The generalized skin depth calculation for a typical porous polarization model is related not only to conductivity, but also to polarization parameters, such as chargeability, characteristic time constant, and frequency dependence. At low-frequency excitation, the generalized skin depth formula can be used to calculate the propagation depth of electromagnetic waves relatively accurately for porous polarized media. This method can be applied to the calculation of electromagnetic wave propagation depths in complex dispersive media. Compared with non-polarized media, in porous polarized media, under low-frequency excitation, the electromagnetic wave propagates deeper, allowing the detection of deeper objects. The data interpretation and imaging of polarized porous media by the generalized skin depth formula have higher accuracy.

The transient electromagnetic method can obtain resistivity and chargeability simultaneously in polarizable medium detection. Typically, we assume that the earth may contain a chargeable medium if the electromagnetic (EM) data appear negative values or sign reversals. Unfortunately, with barely perceptible characteristics, some EM responses with the induced polarization (IP) effects are considered to be non-polarizable responses. Insufficient understanding of features and inaccurate identification of the IP responses limits the use of the IP effects for broader purposes. For these reasons, we perform 1D forward modeling to discuss the degree of EM response affected by the IP effects and to extract polarization characteristics. To identify the IP effects, we combine partial mutual information (PMI) and the fuzzy support vector machine (FSVM) methods to complete the intelligent identification algorithm. We verify the efficiency and practicality of the algorithm by building Debye loops in field experiments. From the analysis, we distinguish the strong and weak IP effects by introducing the impact ratio. The strong IP responses manifest fast decays and sign reversals, and the weak IP responses primarily show fast decays or outward concavity. The identification algorithm validation results show that the recognition accuracy reaches 90.7%. In the field experiment verification, the Debye loop successfully simulates the IP effects of different intensity, and the identification results indicate that the algorithm has potential in the measured data. With this intelligent identification algorithm, the measurements can provide access to the weak polarizable medium when the impact ratio exceeds 30%.

No abstract

Artist's note: So far as I see, poetry not only could express what we see and feel but also might uncover what we neglect. Poems have the power to make unsayable sayable. Moreover, few words and specific patterns (for example, space, blank, and font size) will also help readers sympathize. I was inspired by the "Trump wall," which was known as the Mexico-United States barrier. The wall is both actual and symbolic. The wall is supposed to an architect that provides security and defense. However, in these two poems, I have excavated something out of power and control.I employed antithetic wording in the poem "The Wall 1.0." "I" and "You" are also referring to two different entities that may collide with one another. These opposites highlight irreconcilable relationships. "I" holds the dominant position to legitimate itself while ignoring the counterpart's request. The parallel between the verb and the adjective makes the contrast more distinct. The liveaction crushes the passive description (verb vs. adj.).As for "The Wall 2.0," it is a step-up version of "The Wall 1.0." It is no longer a "conversation" between two parties. The United States claims itself as a land of mighty, purity, and correctness. Mexico, again, is defined and described as a place of evilness. Unlike "(t)he Wall 1.0," in "(t)he Wall 2.0," its passiveness has altered to muteness.

Metal particle cloud is a mixture of micrometersize metal spheres and air. We investigate the electromagnetic wave propagation it and the heat emission of metal cloud. Because of large scattering and low emission in infrared region, it can be applied in airspace technology.