Journal articles: 'Electric properties tomography'

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Hampe, Nils, Max Herrmann, Thomas Amthor, Christian Findeklee, Mariya Doneva, and Ulrich Katscher. "Dictionary-based electric properties tomography." Magnetic Resonance in Medicine 81, no. 1 (September 23, 2018): 342–49. http://dx.doi.org/10.1002/mrm.27401.

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Arduino, Alessandro. "EPTlib: An Open-Source Extensible Collection of Electric Properties Tomography Techniques." Applied Sciences 11, no. 7 (April 4, 2021): 3237. http://dx.doi.org/10.3390/app11073237.

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Electric properties tomography (EPT) is a novel magnetic resonance imaging–based method to estimate non-invasively the distribution of the electric properties in the human body. In this paper, EPTlib, an open-source extensible C++ library collecting ready-to-use algorithms for electric properties tomography, is presented. Currently, EPTlib implements three techniques, named Helmholtz-EPT, convection-reaction-EPT and gradient-EPT, whose derivation and implementation is deeply discussed. Moreover, the configuration files needed by the terminal application included in EPTlib to apply the implemented techniques are outlined. The three techniques are applied to a couple of model problems in order to highlight their main features and the effects of the tunable parameters.

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Katscher, Ulrich, Dong-Hyun Kim, and Jin Keun Seo. "Recent Progress and Future Challenges in MR Electric Properties Tomography." Computational and Mathematical Methods in Medicine 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/546562.

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MR Electric Properties Tomography (EPT) is a lately developed medical imaging modality capable of visualizing both conductivity and permittivity of the patient at the Larmor frequency usingB1maps. The paper discusses the development of EPT reconstructions, EPT sequences, EPT experiments, and challenging issues of EPT.

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Rahimov, Anar, Amélie Litman, and Guillaume Ferrand. "MRI-based electric properties tomography with a quasi-Newton approach." Inverse Problems 33, no. 10 (September 20, 2017): 105004. http://dx.doi.org/10.1088/1361-6420/aa7ef2.

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Jensen, Bjørn Christian Skov, and Kim Knudsen. "Sound speed uncertainty in acousto-electric tomography." Inverse Problems 37, no. 12 (November 26, 2021): 125011. http://dx.doi.org/10.1088/1361-6420/ac37f8.

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Abstract The goal in acousto-electric tomography is to reconstruct an image of the unknown electric conductivity inside an object from boundary measurements of electrostatic currents and voltages collected while the object is penetrated by propagating ultrasound waves. This problem is a coupled-physics inverse problem. Accurate knowledge of the propagating ultrasound wave is usually assumed and required, but in practice tracking the propagating wave is hard due to inexact knowledge of the interior acoustic properties of the object. In this work, we model uncertainty in the sound speed of the acoustic wave, and formulate a suitable reconstruction method for the interior power density and conductivity. We also establish theoretical error bounds, and show that the suggested approach can be understood as a regularization strategy for the inverse problem. Finally, we numerically simulate the sound speed variations from a numerical breast tissue model, and computationally explore the effect of using an inaccurate sound speed on the error in reconstructions. Our results show that with reasonable uncertainty in the sound speed reliable reconstruction is still possible.

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Arduino, A., O. Bottauscio, M. Chiampi, and L. Zilberti. "MRI safety application of the magnetic resonance-based electric properties tomography." Physica Medica 92 (December 2021): S132. http://dx.doi.org/10.1016/s1120-1797(22)00281-2.

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Azzouz, Mustapha, Martin Hanke, Chantal Oesterlein, and Karl Schilcher. "The Factorization Method for Electrical Impedance Tomography Data from a New Planar Device." International Journal of Biomedical Imaging 2007 (2007): 1–7. http://dx.doi.org/10.1155/2007/83016.

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We present numerical results for two reconstruction methods for a new planar electrical impedance tomography device. This prototype allows noninvasive medical imaging techniques if only one side of a patient is accessible for electric measurements. The two reconstruction methods have different properties: one is a linearization-type method that allows quantitative reconstructions; the other one, that is, the factorization method, is a qualitative one, and is designed to detect anomalies within the body.

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Katscher, Ulrich, and Cornelius A. T. van den Berg. "Electric properties tomography: Biochemical, physical and technical background, evaluation and clinical applications." NMR in Biomedicine 30, no. 8 (May 24, 2017): e3729. http://dx.doi.org/10.1002/nbm.3729.

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Arduino, Alessandro, Mario Chiampi, Francesca Pennecchi, Luca Zilberti, and Oriano Bottauscio. "Monte Carlo Method for Uncertainty Propagation in Magnetic Resonance-Based Electric Properties Tomography." IEEE Transactions on Magnetics 53, no. 11 (November 2017): 1–4. http://dx.doi.org/10.1109/tmag.2017.2713984.

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Balidemaj, Edmond, Cornelis A. T. van den Berg, Astrid L. H. M. W. van Lier, Aart J. Nederveen, Lukas J. A. Stalpers, Hans Crezee, and Rob F. Remis. "B1-based SAR reconstruction using contrast source inversion–electric properties tomography (CSI-EPT)." Medical & Biological Engineering & Computing 55, no. 2 (April 23, 2016): 225–33. http://dx.doi.org/10.1007/s11517-016-1497-6.

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Voigt, Tobias, Ulrich Katscher, and Olaf Doessel. "Quantitative conductivity and permittivity imaging of the human brain using electric properties tomography." Magnetic Resonance in Medicine 66, no. 2 (February 24, 2011): 456–66. http://dx.doi.org/10.1002/mrm.22832.

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Straub, André. "Properties of the kernel function in electric stratified problems." GEOPHYSICS 60, no. 6 (November 1995): 1671–81. http://dx.doi.org/10.1190/1.1443899.

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The kernel function plays an important role in the 1-D problem because of the spectral representation of the electric potential for a stratified model with a point source. Functional analysis establishes the equivalence between the differential equation (which governs the kernel function) and a boundary integral equation, called a jump summation equation for the 1-D case. In this equation, the jumps of the weighted Wronskian of two distinct models are summed over all the singular points. Numerous applications of this general equation demonstrate its flexibility. An appropriate choice of models and of the weight function leads to two splitting theorems and two imbedding theorems. The basic idea is to split the stratification into two models for the splitting theorems and into three models for the imbedding theorems. An application of these theorems concerns the handling of underground and underwater sounding measurements. Three possible configurations are examined and their performances are compared. With these examples, a simple method of layer stripping is introduced in the kernel space. These theorems are also used to establish the shift properties for a given set of layers surrounded by two homogeneous half‐spaces. The consequences of these shift properties especially concern electrical tomography, where a case of equivalence is shown. The general character of these theorems may generate other applications.

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Balidemaj, Edmond, Cornelis A. T. van den Berg, Johan Trinks, Astrid L. H. M. W. van Lier, Aart J. Nederveen, Lukas J. A. Stalpers, Hans Crezee, and Rob F. Remis. "CSI-EPT: A Contrast Source Inversion Approach for Improved MRI-Based Electric Properties Tomography." IEEE Transactions on Medical Imaging 34, no. 9 (September 2015): 1788–96. http://dx.doi.org/10.1109/tmi.2015.2404944.

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Li, Xiaonan, Guoqiang Liu, Hui Xia, Lili Hu, Shiqiang Li, Shilong Zhao, and Haiyan Chen. "Investigation in Radio Frequency Magnetic Field Mapping Towards Tissue Magnetic Resonance Electric Properties Tomography." Journal of Medical Imaging and Health Informatics 9, no. 1 (January 1, 2019): 78–83. http://dx.doi.org/10.1166/jmihi.2019.2543.

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Arduino, Alessandro, Francesca Pennecchi, Ulrich Katscher, Maurice Cox, and Luca Zilberti. "Repeatability and Reproducibility Uncertainty in Magnetic Resonance-Based Electric Properties Tomography of a Homogeneous Phantom." Tomography 9, no. 1 (February 17, 2023): 420–35. http://dx.doi.org/10.3390/tomography9010034.

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Uncertainty assessment is a fundamental step in quantitative magnetic resonance imaging because it makes comparable, in a strict metrological sense, the results of different scans, for example during a longitudinal study. Magnetic resonance-based electric properties tomography (EPT) is a quantitative imaging technique that retrieves, non-invasively, a map of the electric properties inside a human body. Although EPT has been used in some early clinical studies, a rigorous experimental assessment of the associated uncertainty has not yet been performed. This paper aims at evaluating the repeatability and reproducibility uncertainties in phase-based Helmholtz-EPT applied on homogeneous phantom data acquired with a clinical 3 T scanner. The law of propagation of uncertainty is used to evaluate the uncertainty in the estimated conductivity values starting from the uncertainty in the acquired scans, which is quantified through a robust James–Stein shrinkage estimator to deal with the dimensionality of the problem. Repeatable errors are detected in the estimated conductivity maps and are quantified for various values of the tunable parameters of the EPT implementation. The spatial dispersion of the estimated electric conductivity maps is found to be a good approximation of the reproducibility uncertainty, evaluated by changing the position of the phantom after each scan. The results underpin the use of the average conductivity (calculated by weighting the local conductivity values by their uncertainty and taking into account the spatial correlation) as an estimate of the conductivity of the homogeneous phantom.

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Gorbach, Dmitriy, Valeriya Yakimenko, and Olga Konovalova. "Application of electric resistivity tomography for investigation of geological situation closed to railways." MATEC Web of Conferences 265 (2019): 03005. http://dx.doi.org/10.1051/matecconf/201926503005.

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The paper reviews methods of engineering geophysics which can be applied to sections of railway tracks. The method of electrical resistivity tomography is used to study the properties of the geological situation under an engineering structure. In the course of practical work, two-dimensional geoelectric sections were obtained. Interpretation of the sections allowed to understand the structure of the near-surface zone.

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Arduino, Alessandro, Mario Chiampi, Luca Zilberti, and Oriano Bottauscio. "Alternative Approaches to Magnetic Resonance-Based Electric Properties Tomography and Local Specific Absorption Rate Estimation." IEEE Transactions on Magnetics 53, no. 2 (February 2017): 1–8. http://dx.doi.org/10.1109/tmag.2016.2621731.

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Gloaguen, Erwan, Bernard Giroux, Denis Marcotte, and Roussos Dimitrakopoulos. "Pseudo-full-waveform inversion of borehole GPR data using stochastic tomography." GEOPHYSICS 72, no. 5 (September 2007): J43—J51. http://dx.doi.org/10.1190/1.2755929.

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Electromagnetic full-waveform tomography is computer intensive and requires good knowledge of antenna characteristics and ground coupling. As a result, ground-penetrating-radar tomography usually uses only the first wavelet’s arrival time and amplitude data. We propose to improve the classical approach by inverting multiple slowness and attenuation fields using stochastic tomography. To do so, we model the slowness and attenuation covariance functions to generate geostatistical simulations that are conditional to the arrival times, amplitudes, slowness, and attenuation observed along boreholes. We combine slowness and attenuation fields to compute conductivity and permittivity fields from which we model synthetic radar traces using a finite-difference time-domain full-waveform algorithm. Modeled traces that best match the measured ones correspond to the computed conductivity and permittivity fields that correlate best with the true physical properties of the ground. We apply the method to a synthetic example with known electric properties. We show that a combination of stochastic tomography and full-waveform modeling allows a better selection of permittivity fields close to the reference field, at a reasonable computing cost.

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Goetz, Georges, Tong Ling, Tushar Gupta, Seungbum Kang, Jenny Wang, Patrick D. Gregory, B. Hyle Park, and Daniel Palanker. "Interferometric mapping of material properties using thermal perturbation." Proceedings of the National Academy of Sciences 115, no. 11 (February 26, 2018): E2499—E2508. http://dx.doi.org/10.1073/pnas.1712763115.

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Optical phase changes induced by transient perturbations provide a sensitive measure of material properties. We demonstrate the high sensitivity and speed of such methods, using two interferometric techniques: quantitative phase imaging (QPI) in transmission and phase-resolved optical coherence tomography (OCT) in reflection. Shot-noise–limited QPI can resolve energy deposition of about 3.4 mJ/cm2 in a single pulse, which corresponds to 0.8 °C temperature rise in a single cell. OCT can detect deposition of 24 mJ/cm2 energy between two scattering interfaces producing signals with about 30-dB signal-to-noise ratio (SNR), and 4.7 mJ/cm2 when SNR is 45 dB. Both techniques can image thermal changes within the thermal confinement time, which enables accurate single-shot mapping of absorption coefficients even in highly scattering samples, as well as electrical conductivity and many other material properties in biological samples at cellular scale. Integration of the phase changes along the beam path helps increase sensitivity, and the signal relaxation time reveals the size of hidden objects. These methods may enable multiple applications, ranging from temperature-controlled retinal laser therapy or gene expression to mapping electric current density and characterization of semiconductor devices with rapid pump–probe measurements.

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Nicolotti, G., L. V. Socco, R. Martinis, A. Godio, and L. Sambuelli. "Application and Comparison of Three Tomographic Techniques for Detection of Decay in Trees." Arboriculture & Urban Forestry 29, no. 2 (March 1, 2003): 66–78. http://dx.doi.org/10.48044/jauf.2003.009.

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This paper reports application of electric, ultrasonic, and georadar tomography for detection of decay in trees and their comparison with the traditional penetrometer. Their feasibility in arboriculture is also evaluated, critically considering some "open problems." The experiments were carried out in an urban environment on two plane (Platanus hybrida Brot.) trees. Both trees, after felling, showed extensive white rot in the central cylinder. The electric tomography revealed low resistivity zones roughly centered in the trunk. A comparison with the successively cut sections showed a fine correspondence to decayed areas and a strong correspondence between high moisture zones and low resistivity zones. Ultrasonic tomography demonstrated to be a very effective tool for the detection of internal decay, accurately locating the position of the anomalies and estimating their size, shape, and characteristic in terms of mechanical properties. With the georadar technique, the high contrast of electromagnetic impedance measured between the inner decayed section and the outside sound section allowed the detection of the interface between the sound and decayed section of the tree, using radar acquisition in reflection modality. The penetrometer profiles detected the low-resistance areas inside the two trunks.

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THA, Khin Khin, Ulrich KATSCHER, Xinnan LI, and Hideki HYODOH. "Noninvasive Assessment of the Cerebrospinal Fluid and Its Composition by Electric Properties Tomography [Presidential Award Proceedings]." Japanese Journal of Magnetic Resonance in Medicine 42, no. 2 (May 15, 2022): 65. http://dx.doi.org/10.2463/jjmrm.2022-1755.

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Chen, Yifan, Chunlong Li, Yosuke Mizuno, Jing Shu, Xiao Xue, Qiang Yuan, Yue Zhao, and Zihan Zhou. "Birefringence tomography for axion cloud." Journal of Cosmology and Astroparticle Physics 2022, no. 09 (September 1, 2022): 073. http://dx.doi.org/10.1088/1475-7516/2022/09/073.

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Abstract An axion cloud surrounding a supermassive black hole can be naturally produced through the superradiance process. Its existence can be examined by the axion induced birefringence effect. It predicts an oscillation of the electric vector position angle of linearly polarized radiations. Stringent constraints of the existence of the axion in a particular mass window has been obtained based on the recent Event Horizon Telescope measurement on M87★. The future Very-Long-Baseline Interferometry (VLBI) observations will be able to measure the vicinity of many supermassive black holes, thus it opens the possibility to search for the existence of axions in a wide mass regime. In this paper, we study how different black hole properties and accretion flows influence the signatures of the axion induced birefringence. We include the impacts of black hole inclination angles, spins, magnetic fields, plasma velocity distributions, the thickness of the accretion flows. We pay special attention to characterize the washout effects induced by the finite thickness of the accretion flows and the lensed photons. Based on this study, we give prospects on how to optimize the axion search using future VLBI observations, such as the next-generation Event Horizon Telescope, to further increase the sensitivity.

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Kim, Soo-Yeon, Jaewook Shin, Dong-Hyun Kim, Min Jung Kim, Eun-Kyung Kim, Hee Jung Moon, and Jung Hyun Yoon. "Correlation between conductivity and prognostic factors in invasive breast cancer using magnetic resonance electric properties tomography (MREPT)." European Radiology 26, no. 7 (October 23, 2015): 2317–26. http://dx.doi.org/10.1007/s00330-015-4067-7.

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Gerke, Björn, Simon-Nis Peters, Nils Marquardt, Christian Huhmann, Volker Michael Hannen, Michael Holtkamp, Uwe Karst, et al. "Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors." Journal of Instrumentation 17, no. 09 (September 1, 2022): P09029. http://dx.doi.org/10.1088/1748-0221/17/09/p09029.

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Abstract Organometallic liquids provide good properties for ionization detectors. TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and Cherenkov photon readout for Positron Emission Tomography. In this work, we present studies for the handling of TMBi at different electric fields and under different environmental conditions to find applicable configurations for the suppression of electrical breakdowns in TMBi at room temperature. A simple glass cell with two electrodes filled with TMBi was constructed and tested under different operation conditions. Working at the vapour pressure of TMBi at room temperature of about 40 mbar and electric fields of up to 20 kV/cm in presence of a small oxygen contamination we found the formation of a discharge channel in the liquid and a steady increase in the current. Further reduction of pressure by pumping caused the TMBi to boil and a spontaneous combustion. Eliminating the oxygen contamination led the TMBi under the same condition to only decompose. When operating the setup under an argon atmosphere of 1 bar we did not observe breakdowns of the electrical potential up to field strengths of 20 kV/cm. Still, in presence of a small oxygen contamination fluctuating currents in the nA range were observed, but no decomposition or combustion. We conclude from our experiments that TMBi at room temperature in a pure argon atmosphere of 1 bar remains stable against electrical breakdown at least up to electric field strengths of 20 kV/cm, presumably because the formation of gaseous TMBi was prevented.

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Jensen-Kondering, Ulf, Liang Shu, Ruwen Böhm, Olav Jansen, and Ulrich Katscher. "In-vivo pilot study at 3 Tesla: Feasibility of Electric Properties Tomography in a rat model of stroke." Physics in Medicine 9 (June 2020): 100024. http://dx.doi.org/10.1016/j.phmed.2019.100024.

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Ceccio, S. L., and D. L. George. "A Review of Electrical Impedance Techniques for the Measurement of Multiphase Flows." Journal of Fluids Engineering 118, no. 2 (June 1, 1996): 391–99. http://dx.doi.org/10.1115/1.2817391.

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Various developments in the use of electrical impedance methods in multiphase flow are reviewed. Because the components of a multiphase flow often exhibit different electrical properties, a variety of probes have been developed to study such flows by measuring impedance in the region of interest. Nonintrusive devices are used to measure spatially averaged flow properties, such as void fraction. Local probes have been developed to measure a variety of pointwise flow quantities, including film thickness in annular flow, local void fraction in dispersed flows, bubble and particle sizes, and flow velocities. Such impedance probes are usually easy to build and use, and can have a high frequency response. However, the spatial resolution of the probes may be limited, calibration may be difficult, and the accuracy of some probes may be limited to specific phase distributions. Researchers are now using electric fields to reconstruct the impedance distribution within a measurement volume via Electrical Impedance Tomography (EIT). EIT systems employ voltage and current measurements on the boundary of a domain to create a representation of the impedance distribution within the domain. EIT inversion algorithms are discussed, and the application of EIT to multiphase flows is reviewed. The benefits and limitations of EIT systems are also discussed.

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Zhang, Lei, and Shaogang Wang. "Correlation of Materials Property and Performance with Internal Structures Evolvement Revealed by Laboratory X-ray Tomography." Materials 11, no. 10 (September 21, 2018): 1795. http://dx.doi.org/10.3390/ma11101795.

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Although X-rays generated from a laboratory-based tube cannot be compared with synchrotron radiation in brilliance and monochromaticity, they are still viable and accessible in-house for ex situ or interrupted in situ X-ray tomography. This review mainly demonstrates recent works using laboratory X-ray tomography coupled with the measurements of properties or performance testing under various conditions, such as thermal, stress, or electric fields. Evolvements of correlated internal structures for some typical materials were uncovered. The damage features in a graded metallic 3D mesh and a metallic glass under mechanical loading were revealed and investigated. Micro-voids with thermal treatment and void healing phenomenon with electropulsing were clearly demonstrated and quantitatively analyzed. The substance transfer around an electrode of a Li-S battery and the protective performance of a Fe-based metallic glass coating on stainless steel were monitored through electrochemical processes. It was shown that in situ studies of the laboratory X-ray tomography were suitable for the investigation of structure change under controlled conditions and environments. An extension of the research for in situ laboratory X-ray tomography can be expected with supplementary novel techniques for internal strain, global 3D grain orientation, and a fast tomography strategy.

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Weigand, Maximilian, and Andreas Kemna. "Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems." Biogeosciences 14, no. 4 (February 28, 2017): 921–39. http://dx.doi.org/10.5194/bg-14-921-2017.

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Abstract. A better understanding of root–soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water–filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.

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Wenger, Cornelia, Hadas Sara Hershkovich, Catherine Tempel-Brami, Moshe Giladi, and Ze’ev Bomzon. "NIMG-41. RAPID AND ACCURATE CREATION OF PATIENT-SPECIFIC COMPUTATIONAL MODELS FOR GBM PATIENTS RECEIVING OPTUNE THERAPY WITH CONVENTIONAL IMAGING (T1w/PD)." Neuro-Oncology 21, Supplement_6 (November 2019): vi170. http://dx.doi.org/10.1093/neuonc/noz175.711.

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Abstract BACKGROUND For understanding the electric field distributions in glioblastoma (GBM) patients receiving OptuneTM therapy computational head models are employed. Accurate and fast model creation is of high importance to patient-specific treatment planning for improving efficacy, i.e., for maximizing intensity delivered to the tumor which depends on the tissues’ electric properties (EPs). Traditional model creation relies on time-consuming tissue segmentation and troublesome binary categorization of distinct tumor areas for assigning homogenous EPs. Here, we present a feasibility study of a new approach for fast model creation that uses individually created, heterogeneous EP maps from conventional MRIs. METHODS In a previous animal study we adapted water-content based electrical properties tomography (wEPT) for creating electrical conductivity (σ) maps at 200 kHz, the operating frequency of OptuneTM therapy. This adapted wEPT approach uses a T1w and a PD image to map the tissues’ water-content (WC) with a simple function. Subsequently the σ map is calculated as a function of WC based on Maxwell’s mixture theory. Three patients of the EF-14 trial were selected for calculating WC and σ maps. One patient was chosen to create a computational head model for simulating OptuneTM treatment. RESULTS The wEPT-estimated values of WC and σ in the healthy brain are accurate, homogenous and consistent among patients. Contrary, wEPT-estimates of WC and σ in tumor tissues are very heterogeneous and variable between patients. The patient-specific model with wEPT reveals more detailed current pathways during OptuneTM therapy. CONCLUSIONS The results emphasize the need for individual head model creation, since binary segmentation masks with pre-defined σ values are not recommended for the heterogeneous and variable tumor. The presented approach holds great promise for rapid creation of patient-specific computational models because only conventional MRIs are needed. However, this method needs to be validated and further established with analyzing more patients.

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Mori, Naoko, Keiko Tsuchiya, Deepa Sheth, Shunji Mugikura, Kei Takase, Ulrich Katscher, and Hiroyuki Abe. "Diagnostic value of electric properties tomography (EPT) for differentiating benign from malignant breast lesions: comparison with standard dynamic contrast-enhanced MRI." European Radiology 29, no. 4 (September 25, 2018): 1778–86. http://dx.doi.org/10.1007/s00330-018-5708-4.

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Wenger, C., H. S. Hershkovich, C. Tempel Brami, M. Giladi, and Z. Bomzon. "Creating Conductivity Maps at 200 Khz of Brain and Tumor Tissue of Glioblastoma Patients with Water-Content Based Electric Properties Tomography." International Journal of Radiation Oncology*Biology*Physics 105, no. 1 (September 2019): S103. http://dx.doi.org/10.1016/j.ijrobp.2019.06.591.

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Dubreuil-Boisclair, Camille, Erwan Gloaguen, Denis Marcotte, and Bernard Giroux. "Heterogeneous aquifer characterization from ground-penetrating radar tomography and borehole hydrogeophysical data using nonlinear Bayesian simulations." GEOPHYSICS 76, no. 4 (July 2011): J13—J25. http://dx.doi.org/10.1190/1.3571273.

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It is known that the heterogeneity of hydraulic conductivity drives the groundwater flow and the transport of contaminants. However, in conventional characterization methods, the lack of densely sampled hydrological data does not permit us to describe the aquifer heterogeneity at an appropriate scale. In this study, we integrate ground-penetrating radar (GPR) tomographic data with hydraulic conductivity logs to estimate the hydraulic conductivity of a heterogeneous unconsolidated aquifer at a decimetric scale between two boreholes. The integration of these different data sets is achieved using a nonlinear Bayesian simulation algorithm. The prior hydraulic conductivity distribution is estimated, under Gaussian hypothesis, by simple kriging of the hydraulic well data. The likelihood of hydraulic conductivity given the relative permittivity and the electrical conductivity functions is obtained from a kernel probability density function estimator that describes the in-situ relationship between the electric and the hydraulic properties measured along boreholes. The proposed method is tested on a synthetic heterogeneous model of permeability to validate the methodology. We show that permeability realizations obtained from the proposed algorithm present a higher correlation with the synthetic model than other classical simulation methods. The method is then applied on data acquired over an unconsolidated aquifer located in Saint-Lambert-de-Lauzon, Quebec, Canada. The data set consists of measurements from (i) GPR crosshole acquisition, (ii) cone penetration testing with pressure measurement combined with soil moisture resistivity, and (iii) a borehole electromagnetic flowmeter. By using the presented Bayesian approach, we generated multiple hydraulic conductivity realizations that are in good agreement with the hydrogeological model of the area.

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Holliger, Klaus, and Tim Bergmann. "Numerical modeling of borehole georadar data." GEOPHYSICS 67, no. 4 (July 2002): 1249–57. http://dx.doi.org/10.1190/1.1500387.

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High‐frequency electromagnetic (EM) wave propagation phenomena associated with borehole georadar experiments are complex. To improve our understanding of the governing physical processes, we present a finite‐difference solution of Maxwell's equations in cylindrical coordinates. This approach allows us to model the full EM wavefield associated with borehole georadar experiments and to assess the adequacy of ray‐based methods currently used to interpret the observed amplitudes. Our results indicate that because shallow boreholes are often water filled, the finite length of the boreholes as well as changes in material properties along a borehole wall can have major effects on the amplitude behavior of borehole georadar data. As a result of waveguide phenomena, the radiation pattern of a vertical electric dipole source located in a water‐filled borehole may be distorted significantly with respect to the corresponding reference radiation pattern in a homogeneous medium. Even greater distortions of the radiation pattern result when the electric dipole source is located near material boundaries or near the upper or lower end of a borehole. This study indicates that some of the basic assumptions of conventional ray‐based amplitude tomography often are not fulfilled for borehole georadar data and that the derived constraints on the attenuation and conductivity structure should be regarded as qualitative in nature. The algorithm and the results presented in this study do, however, offer the perspective to alleviate some of these inherent problems and thus help to make ray‐based georadar attenuation tomography a more reliable and effective tool for probing the shallow subsurface.

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Pašteka, Roman, David Kušnirák, Dennis Wilken, René Putiška, Juraj Papčo, Dominika Godová, Ivan Zvara, Ema Nogová, and Lenka Ondrášová. "Effective combination of microgravimetry and geoelectrical methods in the detection of subsurface cavities in archaeological prospection – selected case-studies from Slovakia." Contributions to Geophysics and Geodesy 49, no. 4 (December 1, 2019): 479–96. http://dx.doi.org/10.2478/congeo-2019-0025.

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Abstract This contribution is focused on a common utilization of microgravimetry (very precise and detailed gravimetry) and geoeletrical methods (ground penetrating radar and electric resistivity tomography) in the detection of subsurface cavities in non-destructive archaeological prospection. Both methods can separately detect such kind of subsurface objects, but their complementary and at the same time an eliminating aspect can be very helpful in the interpretation of archaeogeophysical datasets. These properties were shown in various published case-studies. Here we present some more typical examples. Beside this, we present here for a first time an application of the electric resistivity tomography in the interior of a building (a church) in Slovakia. We also demonstrate an example with an extremely small acquisition step in microgravity as a trial for the detection of cavities with very small dimensions – in this case small separated spaces for coffins as a part of the detected crypt (so called columbarium). Unfortunately, these cavities were too small to be reliably detected by the microgravity method. We have tried the well-known 3D Euler deconvolution method to obtain usable depth estimates from the acquired anomalous gravity field. Results from this method were in the majority of cases plausible (sometimes little bit too shallow), when compared with the results from the ground penetrating radar. In one selected example, the 3D Euler solutions were too deep and in the present stage of study we cannot well explain this situation. In general, all presented results support an important role of common combination of several geophysical methods, when searching for subsurface cavities in non-destructive archaeological prospection.

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Dai, Ya Wen, Zhuo Qiu Li, Xiao Yu Zhang, and Si Rong Zhu. "Virtual Experimental Studies on Carbon Fiber Smart Materials Resistivity Tomography." Advanced Materials Research 79-82 (August 2009): 283–86. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.283.

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With the emergence of large-size complex structures, conventional discrete sensors can’t meet the requirement of structure health monitoring because they can only sense the strain in a single direction. In this paper, based on sensing and covering properties of carbon fiber smart material (CFSM), an idea of a sensitive layer placed on the structure surface was proposed. By setting finite electrodes on the edge of the sensitive layer, the stress field of tested structure is transformed to electric field which is apt to be tested, and with resistivity tomography technology (ERT), field(global) monitoring on civil engineering structure can be realized. To avoid impact resulting from measuring errors caused by misc factors in experiment, CFSM ERT system was utilized in virtual experiments. Virtual Experiments were conducted on ANSYS finite element software aided by its excellent abilities in coupled field analysis. The virtual experiments included two cases: circular plate simply supported at its perimeter under single loading of different values in the center, and circular plate simply supported at its perimeter under multipoint loading in different positions. In the virtual experiments current incentive in adjacent electrodes and voltage measurement in other adjacent electrodes were implemented, and the measured voltage data was transmitted to the ERT system to obtain the contour plot of resistivity distribution. It indicates that for the single loaded CFSM virtual experiment with tensile strain, its resistivity is increased with the load increase. Compared with 1st and 2nd principal strain distribution in structure tested area, resistivity distribution will qualitatively reflect force field of structure. In multipoint loaded CFSM virtual experiment with compress strain, resistivity descends. Compared with 3rd and 2nd principal strain distribution in structure tested area, low resistivity area just locates at area of biggest strain. Based on virtual experiment, efficiency of CFSM ERT system is demonstrated, greatly supporting the consequent practical application.

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Wei, Qiang, Brigitte Leblon, and Armand La Rocque. "On the use of X-ray computed tomography for determining wood properties: a review1This article is a contribution to the series The Role of Sensors in the New Forest Products Industry and Bioeconomy." Canadian Journal of Forest Research 41, no. 11 (November 2011): 2120–40. http://dx.doi.org/10.1139/x11-111.

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In several processes of the forest products industry, an in-depth knowledge of log and board internal features is required and their determination needs fast scanning systems. One of the possible technologies is X-ray computed tomography (CT) technology. Our paper reviews applications of this technology in wood density measurements, in wood moisture content monitoring, and in locating internal log features that include pith, sapwood, heartwood, knots, and other defects. Annual growth ring measurements are more problematic to be detected on CT images because of the low spatial resolution of the images used. For log feature identification, our review shows that the feed-forward back-propagation artificial neural network is the most efficient CT image processing method. There are also some studies attempting to reconstruct three-dimensional log or board images from two-dimensional CT images. Several industrial prototypes have been developed because medical CT scanners were shown to be inappropriate for the wood industry. Because of the high cost of X-ray CT scanner equipment, other types of inexpensive sensors should also be investigated, such as electric resistivity tomography and microwaves. It also appears that the best approach uses various different sensors, each of them having its own strengths and weaknesses.

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Pelech, Ondrej, David Kušnirák, Marián Bošanský, Ivan Dostál, René Putiška, and Jozef Hók. "The resistivity image of the Upper Cretaceous Horné Belice Group: a case study from the Hranty section (Považský Inovec Mts., Western Carpathians)." Contributions to Geophysics and Geodesy 47, no. 1 (March 28, 2017): 23–38. http://dx.doi.org/10.1515/congeo-2017-0002.

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AbstractThe Tatricum crystalline basement in the northern Považský Inovec Mts. contains several narrow tectonic slices with different rock composition. Some of them composed of the Upper Cretaceous mass flow deposits (the Horné Belice Group) are considered unique within the framework of the Internal Western Carpathians and particularly within the Tatricum. Tectonic interpretation of their structural position is longer a matter of debate. Contrasting resistivity properties of the Hercynian mica schists and the Upper Cretaceous sandstones and shales were confirmed by the parametric geophysical measurements. The Hranty section, the structurally highest and most internal Upper Cretaceous tectonic slice was investigated by the electric resistivity tomography. Two longitudinal and two transverse resistivity profiles were measured and combined into a 3D image which suggests that the low resistivity Upper Cretaceous rocks form relatively shallow and flat lying structures folded and deformed between the crystalline basement slices.

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Dafflon, Baptiste, Susan Hubbard, Craig Ulrich, John Peterson, Yuxin Wu, Haruko Wainwright, and Timothy J. Kneafsey. "Geophysical estimation of shallow permafrost distribution and properties in an ice-wedge polygon-dominated Arctic tundra region." GEOPHYSICS 81, no. 1 (January 1, 2016): WA247—WA263. http://dx.doi.org/10.1190/geo2015-0175.1.

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Shallow permafrost distribution and characteristics are important for predicting ecosystem feedbacks to a changing climate over decadal to century timescales because they can drive active layer deepening and land surface deformation, which in turn can significantly affect hydrologic and biogeochemical responses, including greenhouse gas dynamics. As part of the U.S. Department of Energy Next-Generation Ecosystem Experiments-Arctic, we have investigated shallow Arctic permafrost characteristics at a site in Barrow, Alaska, with the objective of improving our understanding of the spatial distribution of shallow permafrost, its associated properties, and its links with landscape microtopography. To meet this objective, we have acquired and integrated a variety of information, including electric resistance tomography data, frequency-domain electromagnetic induction data, laboratory core analysis, petrophysical studies, high-resolution digital surface models, and color mosaics inferred from kite-based landscape imaging. The results of our study provide a comprehensive and high-resolution examination of the distribution and nature of shallow permafrost in the Arctic tundra, including the estimation of ice content, porosity, and salinity. Among other results, porosity in the top 2 m varied between 85% (besides ice wedges) and 40%, and was negatively correlated with fluid salinity. Salinity directly influenced ice and unfrozen water content and indirectly influenced the soil organic matter content. A relatively continuous but depth-variable increase in salinity led to a partially unfrozen saline layer (cryopeg) located below the top of the permafrost. The cryopeg environment could lead to year-round microbial production of greenhouse gases. Results also indicated a covariability between topography and permafrost characteristics including ice-wedge and salinity distribution. In addition to providing insight about the Arctic ecosystem, through integration of lab-based petrophysical results with field data, this study also quantified the key controls on electric resistivity at this Arctic permafrost site, including salinity, porosity, water content, ice content, soil organic matter content, and lithologic properties.

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Giampaolo, Valeria, Paolo Dell’Aversana, Luigi Capozzoli, Gregory De Martino, and Enzo Rizzo. "Optimization of Aquifer Monitoring through Time-Lapse Electrical Resistivity Tomography Integrated with Machine-Learning and Predictive Algorithms." Applied Sciences 12, no. 18 (September 11, 2022): 9121. http://dx.doi.org/10.3390/app12189121.

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In this paper, an integrated workflow aimed at optimizing aquifer monitoring and management through time-lapse Electric Resistivity Tomography (TL-ERT) combined with a suite of predictive algorithms is discussed. First, the theoretical background of this approach is described. Then, the proposed approach is applied to real geoelectric datasets recorded through experiments at different spatial and temporal scales. These include a sequence of cross-hole resistivity surveys aimed at monitoring a tracer diffusion in a real aquifer as well as in a laboratory experimental set. Multiple predictive methods were applied to both datasets, including Vector Autoregressive (VAR) and Recurrent Neural Network (RNN) algorithms, over the entire sequence of ERT monitor surveys. In both field and lab experiments, the goal was to retrieve a determined number of “predicted” pseudo sections of apparent resistivity values. By inverting both real and predicted datasets, it is possible to define a dynamic model of time-space evolution of the water plume contaminated by a tracer injected into the aquifer system(s). This approach allowed for describing the complex fluid displacement over time conditioned by the hydraulic properties of the aquifer itself.

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Kang, Ho-Jung, Ho-Sung Jang, Seong-Hyo Oh, Pil-Hwan Yoon, Gyu-Heun Lee, Jin-Young Park, and Yoon-Suk Choi. "Effect of Injected Oxygen Amount on the Gas Porosity and Mechanical Properties of a Pore-Free Die-Cast Al–Si–Cu Alloy." Metals 11, no. 11 (November 10, 2021): 1805. http://dx.doi.org/10.3390/met11111805.

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With the rise in the demand for eco-friendly and electric vehicles, welding and heat treatment are becoming very important to meet the necessary weight reduction, complexity, and high functionality of die castings. Pore-free (PF) die casting is an effective process that enables heat treatment and welding due to low gas porosities. Indeed, this process affords castings of low gas porosity, similar to those attained by high-vacuum die casting. In this study, we compared the gas porosities of different castings fabricated by PF die casting using varied injected oxygen amounts. The castings were all subjected to T6 heat treatment and analyzed by computed tomography (CT) to compare their microstructure and mechanical properties before and after T6 heat treatment. The results revealed that with the increasing injected oxygen amount, the gas porosity of the specimens decreased while their mechanical properties increased. In particular, the gas porosity was the lowest at 1.26 L. Moreover, the 1.26 L specimen displayed the best tensile strength, yield strength, and elongation results. Finally, Weibull distribution analysis revealed that the tensile strength and elongation repeatability and reproducibility increased with increasing injected oxygen amount.

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Lin, Y‐J, and Suresh V. Venna. "A novel method for piezoelectric transducers placement for passive vibration control of geometrically non‐linear structures." Sensor Review 28, no. 3 (June 27, 2008): 233–41. http://dx.doi.org/10.1108/02602280810882599.

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PurposeThe purpose of this paper is to propose an effective and novel methodology to determine optimal location of piezoelectric transducers for passive vibration control of geometrically complicated structures and shells with various curvatures. An industry‐standard aircraft leading‐edge structure is considered for the actuator placement analysis and experimental verification.Design/methodology/approachThe proposed method is based on finite element analysis of the underlying structure having a thin layer of piezoelectric elements covering the entire inner surface with pertinent boundary conditions. All the piezoelectric properties are incorporated into the elements. Specifically, modal piezoelectric analysis is performed to provide computed tomography for the evaluations of the electric potential distributions on these piezoelectric elements attributed by the first bending and torsional modes of structural vibration. Then, the outstanding zone(s) yielding highest amount of electric potentials can be identified as the target location for the best actuator placement.FindingsSix piezoelectric vibration absorbers are determined to be placed alongside both of the fixed edges. An experimental verification of the aluminum leading edge's vibration suppression using the proposed method is conducted exploiting two resistive shunt circuits for the passive damping. A good agreement is obtained between the analytical and experimental results. In particular, vibration suppression around 30 and 25 per cent and Q‐factor reduction up to 15 and 10 per cent are obtained in the designated bending and torsional modes, respectively. In addition, some amount of damping improvement is observed at higher modes of vibration as well.Research limitations/implicationsThe frequency in the proposed approach will be increased slowly and gradually from 0 to 500 Hz. When the frequency matches the natural frequency of the structure, owing to the resonant condition the plate will vibrate heavily. The vibrations of the plate can be observed by connecting a sensor to an oscilloscope. Owing to the use of only one sensor, not all the modes can be detected. Only the first few modes can be picked up by the sensor, because of its location.Practical implicationsThis method can also be used in optimizing not only the location but also the size and shape of the passive vibration absorber to attain maximum amount of damping. This can be achieved by simply changing the dimensions and shape of the piezoelectric vibration absorber in the finite element model on an iterative basis to find the configuration that gives maximum electric potential.Originality/valueThe determination of optimal location(s) for piezoelectric transducers is very complicated and difficult if the geometry of structures is curved or irregular. Therefore, it has never been reported in the literature. Here an efficient FEA‐based electric potential tomography method is proposed to identify the optimized locations for the PZT transducers for passive vibration control of geometrically complicated structures, with minimal efforts. In addition, this method will facilitate the determination of electric potentials that would be obtained at all the possible locations for piezoelectric transducers and hence makes it possible to optimize the placement and configurations of the candidate transducers on complex shape structures.

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Oyewole, Emmanuel, Mehrnoosh Saneifar, and Zoya Heidari. "Multiscale characterization of pore structure in carbonate formations: Application to the Scurry Area Canyon Reef Operators Committee Unit." Interpretation 4, no. 2 (May 1, 2016): SF165—SF177. http://dx.doi.org/10.1190/int-2015-0123.1.

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Carbonate formations consist of a wide range of pore types with different shapes, pore-throat sizes, and varying levels of pore-network connectivity. Such heterogeneous pore-network properties affect the fluid flow in the formation. However, characterizing pore-network properties (e.g., effective porosity and permeability) in carbonate formations is challenging due to the heterogeneity at different scales and complex pore structure of carbonate rocks. We have developed an integrated technique for multiscale characterization of carbonate pore structure based on mercury injection capillary pressure (MICP) measurements, X-ray micro-computed tomography (micro-CT) 3D rock images, and well logs. We have determined pore types based on the pore-throat radius distributions obtained from MICP measurements. We developed a new method for improved assessment of effective porosity and permeability in the well-log domain using pore-scale numerical simulations of fluid flow and electric current flow in 3D micro-CT core images obtained in each pore type. Finally, we conducted petrophysical rock classification based on the depth-by-depth estimates of effective porosity, permeability, volumetric concentrations of minerals, and pore types using an unsupervised artificial neural network. We have successfully applied the proposed technique to three wells in the Scurry Area Canyon Reef Operators Committee (SACROC ) Unit. Our results find that electrical resistivity measurements can be used for reliable characterization of pore structure and assessment of effective porosity and permeability in carbonate formations. The estimates of permeability in the well-log domain were cross-validated using the available core measurements. We have observed a 34% improvement in relative errors in well-log-based estimates of permeability, as compared with the core-based porosity-permeability models.

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Alumbaugh, David L., and H. Frank Morrison. "Theoretical and practical considerations for crosswell electromagnetic tomography assuming a cylindrical geometry." GEOPHYSICS 60, no. 3 (May 1995): 846–70. http://dx.doi.org/10.1190/1.1443822.

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An iterative Born imaging scheme is employed to analyze the resolution properties of crosswell electromagnetic tomography. The imaging scheme assumes a cylindrical symmetry about a vertical magnetic dipole source and employs approximate forward modeling at each iteration to update the internal electric fields. Estimation of the anomalous conductivity is accomplished through least‐squares inversion. Much of the mathematical formulation of this diffusion process appears similar to the analysis of wavefield solutions, but the attenuation implicit in the complex propagation constant invalidates many of the accepted wavefield criteria for resolution. Images of illustrative models show that vertical resolution improves with increasing frequency and with increased spatial sampling density. In addition, greater conductivity contrasts between the target and the background can result in better resolution. The horizontal resolution depends on the maximum aperture that is employed and with increasing frequency, larger apertures are needed to obtain optimal results. However, the maximum aperture that can be employed, and thus the horizontal resolution, is limited by the rate of attenuation and the noise present in the measurements. Weighting the long‐offset data equally with the zero‐offset data can improve the resolution if the noise is not a function of the dynamic range of the measurement system. At lower frequencies, the resolution can be improved by measuring both the horizontal and vertical components of the magnetic fields. In addition, multiple frequencies can be employed to improve the resolution for limited aperture measurements. The general applicability of the cylindrically symmetric geometry is examined by comparing the 2-D sensitivity functions to those produced by a 2.5-D model, and by imaging a 3-D body with the 2-D iterative Born scheme. For borehole separations greater than five skin depths it is demonstrated that the measurements, and thus the images, are not affected by the geometry of the conductive zone outside of the interwell plane. Thus the 2-D imaging scheme can be employed in these situations. For borehole separations less than five skin depths, artifacts are produced in the images which will lead to faulty interpretations.

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Ranachowski, Zbigniew, Przemysław Ranachowski, Tomasz Dębowski, Tomasz Gorzelańczyk, and Krzysztof Schabowicz. "Investigation of Structural Degradation of Fiber Cement Boards Due to Thermal Impact." Materials 12, no. 6 (March 21, 2019): 944. http://dx.doi.org/10.3390/ma12060944.

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The aim of the present study was to investigate the degradation of the microstructure and mechanical properties of fiber cement board (FCB), which was exposed to environmental hazards, resulting in thermal impact on the microstructure of the board. The process of structural degradation was conducted under laboratory conditions by storing the FCB specimens in a dry, electric oven for 3 h at a temperature of 230 °C. Five sets of specimens, that differed in cement and fiber content, were tested. Due to the applied heating procedure, the process of carbonization and resulting embrittlement of the fibers was observed. The fiber reinforcement morphology and the mechanical properties of the investigated compositions were identified both before, and after, their carbonization. Visual light and scanning electron microscopy, X-ray micro tomography, flexural strength, and work of flexural test Wf measurements were used. A dedicated instrumentation set was prepared to determine the ultrasound testing (UT) longitudinal wave velocity cL in all tested sets of specimens. The UT wave velocity cL loss was observed in all cases of thermal treatment; however, that loss varied from 2% to 20%, depending on the FCB composition. The results obtained suggest a possible application of the UT method for an on-site assessment of the degradation processes occurring in fiber cement boards.

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Basak, Anirban, Pratik Brahma, and Bhaskaran Muralidharan. "Momentum relaxation effects in 2D-Xene field effect device structures." Journal of Physics D: Applied Physics 55, no. 7 (November 12, 2021): 075302. http://dx.doi.org/10.1088/1361-6463/ac3354.

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Abstract We analyze the electric field driven topological field effect transition on 2D-xene materials with the addition of momentum relaxation effects, in order to account for dephasing processes. The topological field effect transition between the quantum spin Hall phase and the quantum valley Hall phase is analyzed in detail using the Keldysh non-equilibrium Green’s function technique with the inclusion of momentum and phase relaxation, within the self-consistent Born approximation. Details of the transition with applied electric field are elucidated for the ON–OFF characteristics with emphasis on the transport properties along with the tomography of the current carrying edge states. We note that for moderate momentum relaxation, the current carrying quantum spin Hall edge states are still pristine and show moderate decay with propagation. To facilitate our analysis, we introduce two metrics in our calculations, the coherent transmission and the effective transmission. In elucidating the physics clearly, we show that the effective transmission, which is derived rigorously from the quantum mechanical current operator is indeed the right quantity to analyze topological stability against dephasing. Exploring further, we show that the insulating quantum valley Hall phase, as a result of dephasing carries band-tails which potentially activates parasitic OFF currents, thereby degrading the ON–OFF ratios. Our analysis sets the stage for realistic modeling of topological field effect devices for various applications, with the inclusion of scattering effects and analyzing their role in the optimization of the device performance.

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Hiller, Daniel, Julian López-Vidrier, Keita Nomoto, Michael Wahl, Wolfgang Bock, Tomáš Chlouba, František Trojánek, et al. "Absence of free carriers in silicon nanocrystals grown from phosphorus- and boron-doped silicon-rich oxide and oxynitride." Beilstein Journal of Nanotechnology 9 (May 18, 2018): 1501–11. http://dx.doi.org/10.3762/bjnano.9.141.

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Phosphorus- and boron-doped silicon nanocrystals (Si NCs) embedded in silicon oxide matrix can be fabricated by plasma-enhanced chemical vapour deposition (PECVD). Conventionally, SiH4 and N2O are used as precursor gasses, which inevitably leads to the incorporation of ≈10 atom % nitrogen, rendering the matrix a silicon oxynitride. Alternatively, SiH4 and O2 can be used, which allows for completely N-free silicon oxide. In this work, we investigate the properties of B- and P-incorporating Si NCs embedded in pure silicon oxide compared to silicon oxynitride by atom probe tomography (APT), low-temperature photoluminescence (PL), transient transmission (TT), and current–voltage (I–V) measurements. The results clearly show that no free carriers, neither from P- nor from B-doping, exist in the Si NCs, although in some configurations charge carriers can be generated by electric field ionization. The absence of free carriers in Si NCs ≤5 nm in diameter despite the presence of P- or B-atoms has severe implications for future applications of conventional impurity doping of Si in sub-10 nm technology nodes.

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Grant, Alex, and Colm O'Dwyer. "Real-time nondestructive methods for examining battery electrode materials." Applied Physics Reviews 10, no. 1 (March 2023): 011312. http://dx.doi.org/10.1063/5.0107386.

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With the importance of Li-ion and emerging alternative batteries to our electric future, predicting new sustainable materials, electrolytes, and complete cells that safely provide high performance, long life, and energy dense capability is critically important. Understanding the interface, the microstructure of materials, and the nature of electrolytes and factors that affect or limit long-term performance is key to new battery chemistries, cell form factors, and alternative materials. The electrochemical processes `that cause these changes are also difficult to probe because of their metastability and lifetimes, which can be of nanosecond to sub-nanosecond time domains. Consequently, developing and adapting high-resolution, nondestructive methods to capture these processes proves challenging, requiring state-of-the-art techniques. Recent progress is very promising, where optical spectroscopies, synchrotron radiation techniques, and energy-specific atom probe tomography and microscopy methods are just some of the approaches that are unraveling the true internal behavior of battery cells in real-time. In this review, we overview many of the most promising nondestructive methods developed in recent years to assess battery material properties, interfaces, processes, and reactions under operando conditions similar in electrodes and full cells.

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Abudeif, Abdelbaset M., Gamal Z. Abdel Aal, Nessreen F. Abdelbaky, Ahmed M. Abdel Gowad, and Mohammed A. Mohammed. "Evaluation of Engineering Site and Subsurface Structures Using Seismic Refraction Tomography: A Case Study of Abydos Site, Sohag Governorate, Egypt." Applied Sciences 13, no. 4 (February 20, 2023): 2745. http://dx.doi.org/10.3390/app13042745.

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Because of the strategic importance of the Abydos archaeological site in Egypt as a source of wealth for Egyptian tourism, this study was concerned with carrying out geophysical measurements to detect subsurface succession and measure variations in the geotechnical engineering features of the soils/rocks in order to protect this significant area. The findings will assist geologists and seismologists in collaborating with archaeologists for future site development, revitalization, and investment. The primary objectives of this work were to determine the subsurface lithology, evaluate the engineering geotechnical properties of soils/rocks, identify the layer thicknesses, and identify the site class by calculating Vs30. To achieve these goals, seventeen (17) seismic refraction tomography (SRT) P- and S-wave measurements were executed in front of the Osirion location. SeisImager Software was used for the processing and interpretation of the outcomes. The results were the travel time–distance curves, which were used for building the 2D seismic models that exhibited the velocity and the depth of the layered models. These models were validated by our previous works using electric resistivity tomography and borehole data. The results indicated that this site consisted of three geoseismic subsurface layers. The first layer was the surface that was made up of wadi deposits, which were a mixture of gravel, sand, and silt and were characterized by incompetent to slightly competent materials. The second layer corresponded to the sand and muddy sand deposits of competent rock that was of fair to moderate quality. The third layer (clay deposits) had a higher velocity and was more compact and may be employed as a bedrock layer. The elastic moduli, Vs30, petrophysical, and geotechnical properties of the three geoseismic layers were appraised as essential parameters. Integration of petrophysical and geotechnical parameters and elastic moduli revealed that the third layer was composed of competent clays, which were characterized by low values of porosity, void ratio, Poisson ratio, and stress ratio. It also had a high rigidity, Young’s and bulk moduli, concentration and material indexes, N-value, ultimate bearing capacities, and high density values, and vice versa for the first layer. The standard NEHRP site class was B (rocks). These parameters are ordinarily used as key indications and serve as significant inputs for any future work.

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Pettinelli, Elena, Stan E. Beaubien, Annalisa Zaja, Antonio Menghini, Nicola Praticelli, Elisabetta Mattei, Andrea Di Matteo, Aldo Annunziatellis, Giancarlo Ciotoli, and Salvatore Lombardi. "Characterization of a C O2 gas vent using various geophysical and geochemical methods." GEOPHYSICS 75, no. 3 (May 2010): B137—B146. http://dx.doi.org/10.1190/1.3420735.

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An understanding of gas migration along faults is important in many geologic research fields, such as geothermal exploration, risk assessment, and, more recently, the geologic storage of man-made carbon dioxide [Formula: see text]. If these gases reach the surface, they typically are discharged to the atmosphere from small areas known as gas vents. In a study of an individual gas vent located in the extinct Latera caldera, central Italy, near-surface geochemical and geophysical surveys were conducted to define the spatial distribution of gas-induced effects in the first few meters of the soil and, by inference, the 3D structure and geometry of the associated gas-permeable fault. Grid surveys and detailed profiles were performed across this vent using time-domain reflectometry (TDR), ground-penetrating radar (GPR), frequency-domain electromagnetics (FDEM), electrical resistivity tomography (ERT), and gas geochemistry measurements. Detailed profilesurveys indicate that the leaking [Formula: see text] has changed the physical, chemical, and biological soil environment of the vent, resulting in significant spatial variations in parameters (e.g., water content and soil electric/dielectric properties) that influence geophysical measurement results. Despite the strong difference in vertical and lateral resolution and depth of investigation, all methods show the same general trends and similar relative variations in the measured physical parameters. TDR and GPR data highlight anomalous shallow lateral variations, whereas FDEM and ERT measurements identify the vertical extension of the anomalous zone. All methods highlight a north-northwest–south-southeast anomaly alignment that we associate with the main fault; FDEM and, to a lesser extent, [Formula: see text] flux also show elongation orthogonal to this direction, implying that the vent may occur at the intersection of two structures. Thus, different near-surface geophysical and geochemical methods can provide important information on faults and their gas-migration characteristics.

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FOMENKO, Nikolay, Natalia BOROVIK, Dmitriy GAPONOV, and Ludmila FOMENKO. "APPLICATION OF ELECTRIC EXPLORATION AND ATMOGEOCHEMICAL TECHNOLOGIES IN SEISMIC MICROZONING OF A TUNNEL JUNCTION THROUGH THE MARKOTKH RIDGE." Sustainable Development of Mountain Territories 12, no. 4 (December 30, 2020): 542–54. http://dx.doi.org/10.21177/1998-4502-2020-12-4-542-554.

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Aim. Investigation of the electrical exploration effectiveness and atmogeochemical technologies for detecting discontinuous and folded tectonic disturbances during seismic microzoning of the tunnel crossing over the "Markotkhsky ridge" Task. Study of the tectonic disturbance degree and flooding of the flysch strata using spatial electrical filtration, electropotential tomographic sensing, and atmogeochemical measurements along the tunnel route using data from route surveys and drilling at the tunnel design site. Research methods. 1) Field electrical survey measurements of spatial electrical filtration and electropotential tomographic sensing and with installations of multidirectional electric field excitation for" highlighting " target objects. 2) Using a multi-variant system for presenting field data in the form of tomograms and in the form of electro-profiling and sounding to identify destructive zones related to tectonically disturbed rocks and flood zones. Research results. The analysis of domestic and foreign publications on the use of electrical exploration methods in seismic microdistricting of design, construction and operation of critical facilities is performed. On the example of a tunnel crossing over the Markotkhski ridge: 1) geological, geo-ecological, and seismological characteristics of the area of engineering and geophysical research are considered; 2) the field studies of spatial technologies electric filtrazione, electropotentials tomographic probing and atmogeochemical of observations are produced; 3) the heterogeneity of fliteway thickness laterally and quasioperational this thickness on the electrical properties at depth is shown; 4) as a result poperechnogo analysis curves electropotentials tomographic probing, as well as charts of the spatial electric filtrational and atmogeochemical measurements of an tectonically disturbed and watery areas are identified; 5) the degree of differentiation of the flysch thickness by the values of the specific electrical resistance was estimated using a pseudo-section constructed in the Res2Dinv program. Conclusions. The technologies of electropotential tomographic sounding and spatial electric filtration are unique in terms of mobility and simplicity of field measurements, subsequent geological and geophysical interpretation of anomalous values of the electric field based on its redistribution in tectonically and technogenically disturbed geological structures. The result is the identification of places of development of tectonic discontinuities and watered zones, information about which makes it possible to predict, along with the seismicity of the rock mass inside the tunnel, possible places of potential collapse and flooding during the design, construction and subsequent operation of tunnel crossings. A significant achievement of the experiments can be attributed to the identification of the possibility of electroprobing the flysch strata with steeply-and obliquely-lying layers by dipole electric exploration installations. The proof is that the growth of the right branches of the probing curves does not exceed 45°. Consequently, the steeply-and obliquely-lying flysch strata can be considered heterogeneous laterally and quasihomogeneous in depth in terms of electrical properties.

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Journal articles on the topic 'Electric properties tomography'

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