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The influence on sample preparation on spectral induced polarization of unconsolidated sediments
摘要： Spectral induced polarization (SIP) measurements in the laboratory are in many cases intended to provide representative and comparable results of complex electrical conductivity. This is not invariably the case when using unconsolidated sediments, as the sample preparation influences several SIP-relevant properties of the samples, including the pore geometry. The pore space is supposed to control the polarization effect and therefore a change in the pore space will change the measured parameters. We analysed the influence of the sample preparation on SIP measurements by testing various filling methods, each defined by a sequence of particular steps, with regard to the reproducibility of the spectra. The measurements were performed on three different sample materials. Variations of the spectra due to different filling methods were obtained, indicating the importance of considering the sample preparation. Methods that improved the reproducibility compared to loose packing of the samples were found, but the most suitable packing procedure depended on the material properties. The mean relaxation times and normalized chargeabilities were obtained from a Debye decomposition. Although unidentified processes caused scattering of the measured parameters, a relation of the IP-parameters to the porosities was present. A decrease of the porosity reduced both the relaxation times and the normalized chargeabilities.
关键词： Debye decomposition,sample preparation,unconsolidated sediments,reproducibility,spectral induced polarization,porosity
更新于2025-09-23 15:22:29
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Nonlinear Fiber Optics || Pulse propagation in fibers
摘要： For an understanding of the nonlinear phenomena in optical ?bers, it is necessary to consider the theory of electromagnetic wave propagation in dispersive nonlinear media. The objective of this chapter is to obtain a basic equation that governs propagation of optical pulses in single-mode ?bers. Section 2.1 introduces Maxwell’s equations and important concepts such as the linear and nonlinear parts of the induced polarization and the frequency-dependent dielectric constant. The concept of ?ber modes is introduced in Section 2.2 where the single-mode condition is also discussed. Section 2.3 considers the theory of pulse propagation in nonlinear dispersive media in the slowly varying envelope approximation with the assumption that the spectral width of the pulse is much smaller than the frequency of the incident radiation. The numerical methods used to solve the resulting propagation equation are discussed in Section 2.4.
关键词： electromagnetic wave propagation,dispersive nonlinear media,numerical methods,nonlinear phenomena,optical fibers,single-mode fibers,fiber modes,pulse propagation,dielectric constant,induced polarization,Maxwell’s equations
更新于2025-09-12 10:27:22
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Sensing coated iron-oxide nanoparticles with spectral induced polarization (SIP): Experiments in natural sand packed flow-through columns
摘要： The development of nanoparticle-based soil remediation techniques is hindered by the lack of accurate in situ nanoparticle (NP) monitoring and characterization methods. Spectral induced polarization (SIP), a non-invasive geophysical technique, offers a promising approach to detect and quantify NPs in porous media. However, its successful implementation as a monitoring tool requires an understanding of the polarization mechanisms, the governing NP-associated SIP responses and their dependence on the stabilizing coatings that are typically used for NPs deployed in environmental applications. Herein, we present SIP responses (0.1-10,000 Hz) measured during injection of a poloxamer-coated super-paramagnetic iron-oxide nanoparticle (SPION) suspension in flow-through columns packed with natural sand from the Borden Aquifer. An advective-dispersive transport model is fitted to outflow SPION concentration measurements to compute average concentrations over the SIP spatial response domain (within the columns). The average SPION concentrations are compared with the real and imaginary components of the complex conductivity. Excellent correspondence is found between the average SPION concentrations the columns and the imaginary conductivity values, suggesting that NP-mediated polarization (that is, charge storage) increases proportionally with increasing SPION concentration. Our results support the possibility of SIP monitoring of spatial and temporal NP distributions, which can be immediately deployed in bench-scale studies with the prospect of future real-world field applications.
关键词： Maxwell-Wagner polarization,relaxation time,super paramagnetic iron-oxide nanoparticles (SPIONs),Spectral induced polarization (SIP),chargeability
更新于2025-09-09 09:28:46
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One-particle density matrix polarization susceptibility tensors
摘要： The electric field-induced change in the one-electron density has been expressed as a series of the one-particle density matrix susceptibilities interacting with the spatial distribution of the electric field. The analytic approximate expressions are derived at the Hartree-Fock theory, which serves as a basis for the construction of the generalized model that is designed for an arbitrary form of wavefunction and any type of one-particle density matrix. It is shown that it is possible to accurately predict the changes in the one-electron ground-state density of water molecule in a spatially uniform electric field, as well as in spatially non-uniform electric field distribution generated by point charges. When both linear and quadratic terms with respect to the electric field are accounted for, the electric field-induced polarization energies, dipole moments, and quadrupole moments are quantitatively described by the present theory in electric fields ranging from weak to very strong (0.001–0.07 a.u.). It is believed that the proposed model could open new routes in quantum chemistry for fast and efficient calculations of molecular properties in condensed phases.
关键词： polarization susceptibility tensors,one-particle density matrix,quantum chemistry,Hartree-Fock theory,electric field-induced polarization
更新于2025-09-09 09:28:46
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Nondestructive Testing for Archaeology and Cultural Heritage (A Practical Guide and New Perspectives) || Nondestructive Testing Technologies for Cultural Heritage: Overview
摘要： In this chapter, the most used NDT geophysical technologies applied in the field of preventive archaeology and in the analysis of monumental heritage will be considered. Starting from the current state of the art, we will examine: Ground-Penetrating Radar (GPR), electrical active (Electrical Resistivity Tomography—ERT; induced polarization—IP) and passive (Self-Potential—SP), and seismic sonic an ultrasonic methods. Here some important theoretical aspect will be explained as simply as possible, also using practical examples.
关键词： Monumental Heritage,Preventive Archaeology,Induced Polarization,Electrical Resistivity Tomography,Geophysical Technologies,Seismic Sonic,Self-Potential,Ground-Penetrating Radar,Nondestructive Testing,Ultrasonic Methods
更新于2025-09-09 09:28:46